Obviously there are two cases here: VFR and IFR.
In VFR, flying above a layer is OK if you can be sure there is a “hole” down route, but flying between layers will place you in IMC if the two layers close up. Also ATC may not clear you into some airspace which you would need to remain VMC.
In IFR, the normal objective is to fly VMC on top regardless of how high one has to go to do that (subject only to aircraft performance and whether you carry oxygen) and airspace/ATC are almost never an issue. So if you are between layers, they might close up and then you could be heading for icing conditions, convective wx, or both. And the aircraft performance may not allow a climb (cloud above too thick, or icing conditions) and a descent may create a terrain conflict as well as undesirable other stuff like dropping out of CAS and (in some countries) losing the IFR clearance. So flying between layers is clearly not a good idea unless the layer above is obviously thin and you could climb above if you had to.
How do others manage this stuff?
Ice protection systems on most light GA planes cannot handle sustained icing conditions.
It depends on the situation.
VFR I would definitly accept layers which have a decent altitude difference in between. E.g. an AC layer at a 10’000 ft base with an LC layer with a top of maybe 3000-4000 ft below, preferrably sct or bkn to overcast. The lower layer should not be sitting on the ground but have a at least 1000 ft ceiling below if i fly SE.
IFR, between layers is a very good possibility to fly in VMC conditions when there is considerable murk below and above. I would definitly try to find out where the clear layer is and plan my flight at that level if possible.
Very interesting.
I found myself in exactly this situation on Sunday, returning from Pembrey (random change of plan on Saturday as the Isle of White was fogged in when the rest of the country was in glorious sunshine!) where I remained in between layers in full IMC for a good hour.
Having climbed to 5000’ in search of better conditions, there was no immediate sign of sunlight above and with OAT showing 0 celsius, I feared potential icing so descended to ‘warmer’ air a thousand feet below where performance felt a lot better (maybe my imagination but I prefer to trust my instincts). The options for any further descending ran out at that point as I was now above the Welsh mountains 
So there I stayed. Once able to descend further, Brize gave me an IFR transit at 3200’ but still in between layers and challenging wx until Bovingdon when the skies finally opened up. Phew…
I imagine this situation must be very common – damned if you climb or descend, so you just sit it out, and focus?
For IFR I don’t see much difference between flying between layers or on top. Just as the layers could close in on you, the cloud tops could rise above the climb performance of your aircraft.
Airborne_Again wrote:
Just as the layers could close in on you, the cloud tops could rise above the climb performance of your aircraft.
Very true.
In my opinion IFR between layers is fine. I do it often and most of the time without any problems. Icing is not that often as someone might supose. I was flying a PA28 without Tks for more then 300 hours ifr and had two times serious icing with followig decent. Most of the time I had to fly in clouds or in between layers due of non turbo. If there is a way out with a decent into warmer temperatures no factor. And ATC always cleared us immediately for lower.
Peter wrote:
In IFR, the normal objective is to fly VMC on top regardless of how high one has to go to do that
Is it? I’m happy to stay IMC in cloud as long as it is not freezing or convective for a short – medium period of time…
I happily fly IFR between the layers if I know what’s above me 
If I can expect freezing rain from above then it’s obviously bad decision. In general, it’s again about preparing the flight – if you’re aware of forecasted weather and know how much it can deteriorate you’re in position to make informed decision. Using any additional resource (radar and IR in-flight images, ATC info, PIREPs) is also beneficial. I was once flying at FL120 between the layers thinking that cloud above was too thick when airliner which departed few minutes before me, informed me that sky was clear at FL160 with tail wind as additional bonus. On the other occasion I got info from ATC (consistent with my ADL120) that it was too thick and not worth of trying to out climb because I was about to exit it in 5 minutes.
Thanks Emir – yet another compelling reason for me to invest in a Golze unit
For me, who only flys VFR, I’ve pretty much given up flying between layers. If they are 10k feet apart then I don’t really see it as “between”. But layers that are a few thousand feet apart always seem to close up on my and I end up back tracking to get back down.
