Hello all.
I was trying to import some of my favourites FS2k2planes in CFS2 and got stuck on two weird problems:

1) Daviator Stearman : model shows correctly, but can't gain enough speed to take off(no more than 50 kts at full throttle).

2)Civil DC4 (two different models, one GMax converted and one non-GMax): both planes show but immediately begin to spin violently and become uncontrollable (this happens both when starting flight on the ground or already airborne).

I'm no expert on air files and such, so I've no clue. Both planes fly of course perfectly in FS2k2.
Any help? Thanks in advance...  ???