The spar issue is simply one of serial numbers, the early Aircraft did not have a problem as do the later ones and the SB clearly sets this out.
The propellor issue is clearly one that favours the fixed pitch prop if you are looking for cruise performance, the MT retrofit props are aimed at the German glider tug requirement to increase the takeoff and climb performance at the expense of cruse performance, the different exhaust system required with these props may also have an effect as these are attractors of drag.
As most of these CS props had been approved a long time back I think there is reason to re-visit the subject with the latest blade technology but it is doubtfull if this will stack up economicly, I guess it may be time to start looking at the £/$ rate to find the most favourable time to buy a new Sensenich.
Of course it all depends on the wear and tear of your prop, but Sensenich can be overhauled / zerotimed for a fraction of price of a new one. It’s a simple procedure. I know some people who have chosen cut the costs even further by polishing, re-painting and rebalancing their props. They are certainly missing the very nice “Sensenich” stickers and form one, but performance wise there is little difference.
My Aircraft was fitted with a compromise prop by the last owner and while I was based at a smallish private strip I was not inclined to change a prop that gave me the ability to lift the payload safely off the ground while returning reasonable cruise performance.
Having moved to an airfield with longer runways take off performance is now much less critical so the cruise prop that is the normal fit for the Regent is very much on the agenda. I have managed to get a copy of the MT E-435 flight manual amendment and this shows nothing to be gained in the cruise performance as like most of the offerings for the DR400-180 it is aimed at making a glider tug a passable touring Aircraft.
