Seb,

Does the aircraft have animated u/c "suspension", if so you may need to tone down the sensitivity of the  u/c damper or damping ratio numbers.  These data are around the middle of the contact point line for each u/c leg.  I can't remember where exactly offhand, but the MS SDK will tell you.

Did you convert the whole plane and retained the FS9 .air and aircraft.cfg files  or have you mated the visual model to an existing FS2002 flight dynamics set ?  there are some differences between these files in the two sims.  I usually try to retain the FS2002 files which I know work.

There could be other aspects of the contact points such as wrong static height or static pitch.  If the plane zooms off the ground when coming out of slew mode, that's a sure sign one or more of those parameters are wrong.

It may be a good case of trial & error but make backups as you go !!!!
Degsy