Emir, it's always an option to just 'stick' with your full TKS TB20. It's such an excellent euro IFR tourer.
What are you looking to get with a DA42, which you aren't getting in your TB20? (and no, that's not a wink-wink 
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What are you looking to get with a DA42, which you aren't getting in your TB20?
Twin engine above everything and Jet A1 as an additional benefit. And I don't see some 100LL twin (like Seneca or Baron) as alternative.
I look at the DA42 also.
The feeling I get, speaking to various people involved in the maintenance, is that you will lose a big chunk of the maintenance flexibility you have on the TB20, which is a simple plane really and is very easy to work on (by anybody with more than half a brain).
On the TB20, one is not reliant on Socata except for airframe parts, and one doesn't need those in any significant quantity/cost unless the airframe is well shagged (through abuse, corrosion, or lack of lubrication during maintenance). And one could say the same for any Lyco engined plane...
Whereas with the DA42 one is a lot more reliant on Diamond for service support. I don't suppose there are many bits you could just buy mail order from the USA...
The degree to which that matters depends on the extent to which one micro-manages one's maintenance. Most owners don't get involved at all. And Zagreb is not very far from Austria!
But one could make that argument against anything "modern"
I am still waiting to hear what the Diamond warranty actually says, regarding whether the engines come (or attempt to come) with a separate warranty.
Whereas with the DA42 one is a lot more reliant on Diamond for service support.
My current mechanic used to work in Diamond factory and used to service DA20 and DA40 (including TDI) when Diamond had flying school in Croatia. I believe he still services some DA20's and I'm sure he wears Diamond's overalls :) when he changes the oil. He was certified for Thielert 1.7 engine and he doesn't have high opinion about it while he doesn't have much knowledge about 2.0 and Austro.
BTW There are some plans in Diamond to open service facility at LDVA in near future.
As to maintenance, my experience is not bad, after having flown almost 6 year in a DA42. Of course, the Thielert issue also caught me, although sofar basically only scheduled maintenance, see my earlier post on costs.
Airframe wise I have not had any real issues. I must say though that many metal parts were not designed to live where I live, a hot, salty and humid place. I am talking hinges, bolts and nuts. My plane lives inside now luckily but many such parts had to be replaced. Diamond did a good job doing that under warranty. Better yet, they recommended the ample use of a corrosion inhibitor, sticky stuff that you can apply with a little brush and does an outstanding job of conservation. Something any owner can easily do himself.
Another thing also stands out, the quality of the paint work. I had a good polishing/waxing job done last year and it looks as new.
I believe that in the end there must be an advantage in terms of maintenance of a composite plane vs a metal one, isn't that one of the key things why the shift is made in this industry?
I must say though that many metal parts were not designed to live where I live, a hot, salty and humid place. I am talking hinges, bolts and nuts. My plane lives inside now luckily but many such parts had to be replaced.
I had heard exactly that too, but didn't want to mention it as it came from just one maintenance outfit. They said a lot of metal parts had rusted within a year, from new. So on every Annual they were replacing a lot of metal brackets and similar parts.
Having said that, their customers were based on the UK coast, non-hangared.
Diamond did a good job doing that under warranty.
The problem is that once their warranty expires (2 years?) you will be left replacing all the rusting bits yourself.
Better yet, they recommended the ample use of a corrosion inhibitor, sticky stuff that you can apply with a little brush and does an outstanding job of conservation.
There are products such as LPS, and ACF-50 for voids which are reasonably protected from airflow etc, but why can't Diamond use better quality plating on metal components?
The feeling I get, speaking to various people involved in the maintenance, is that you will lose a big chunk of the maintenance flexibility you have on the TB20, which is a simple plane really and is very easy to work on
The mission of light aircraft makes this important as a design requirement. The raison d'etre of a light aircraft is to get the owner to places typically not well served by infrastructure - unlike light jets that are intended to fly between major airports.
European manufacturers (of anything) do tend to overlook the infrastructure and practicality issue. Another example is the historical tendency of Italian motorcycle manufacturers to fit a fuel tank with no more than 150 miles range (they simply could not believe is was necessary), and for BMW's maintenance philosophy to assume there's a dealer on every corner with all their diagnostic equipment on hand. You could say the same thing I suppose about US aircraft manufacturers and 100LL fuel, but exchanging one problem (fuel availability) for another (maintenance infrastructure requirement) still leaves you without a complete solution.
Re corrosion - Its really the toughest thing, isn't it? I chose my base with dry climate in mind, further from my house but drier.
Someone asked about a 155hp retrofit with the 2.0 engines. I understand that there is one individual who is pursuing this option as an STC.
That STC will be an impressive feat, because a more powerful engine is bound to make the plane go faster... that is a LOT of recertification.
When Socata did the TB "GT" in 1999 or so, they laboriously avoided changing the book performance of the plane, by using retracting footrests to regain the speed lost by the increase in cockpit volume (the domed roof) and - using a fudge which would make any engineer roll all over the floor - by printing the same 1988 POH for the new plane, and calling the "GT" version - wait for it - "Modification 151". But, hey, it's the same plane so no need to recertify; their DGAC design authority meant it could be signed off more or less internally.
That project (I didn't do much reading) is either being done by real industry-insider professionals or it is being done by somebody rather hopeful...
What is customary with turboprop conversions (where you have a lot more HP) is that you set the Vne at the top of the yellow arc (I believe the certification authority forces that, usually) and then you end up with a "slower" plane, unless you always fly at FL250+ in which case the TAS becomes quite respectable again. The Jetprop is one example.
