I've tried the Cub, B17 & B377 in Prepar3D and they do work OK but with a couple of problems.
First off all plane settings seem to be shared between FSX and P3D so if you take a flight in FSX then later load the same plane in P3D it will be in the same state it was in when you finished flying it in FSX (and visa-versa).
At first I thought this a problem but after a while I decided I like it. In fact if A2A where planing to release some sort of migrator it might be worth including an option to keep them synced or separate them (hint hint).
Secondly but linked to the above the controller config program doesn't work correctly in P3D, (not a problem in the Cub as it doesn't have one).
As above it doesn't matter if you set them with the FSX or P3D install, they'l be saved in both.
The big problem is although everything work OK in FSX, in P3D any axis only work over about 50% of there range.
For instance I like to setup the twist on my X52 as the AP bank handle, in FSX I can bank left and right perfectly but in P3D I can only bank right
As for installing the Cub, 377 and Accu-feel all install directly to P3D as long as you first place a copy of your FSX.exe in the Prepar3D folder. Once there installed you have to manually copy the dll.xml entries over from FSX to P3D.
The B17 and 3D lights wouldn't install directly and I had to copy them over manually but worked OK after that.
C2D Q9650 @3.6
8Gb Corsair Vengeance DDR3 PC3-12800C9 1600MHz
Akasa 1000w PSU
Antec 1200 gaming case
Asus VE276Q 27" Monitor 1920x1080
Win 7 Home Premium 64bit SP1