First all converting is an dark art of some kind.
Have never gone from CFS2 to FS04 but I have read about it and add missing entries into the aircraft.cfg seem to be what is needed most of the time.
When you converted to FS04 did you use the aircraft.cfg from and FS04 B-17? CFS2 [contact_points] should work in FS04. If you didn't change the [contact_points] from those I made for the canard B-17 make sure that the nose gear is still there by taking off IF you can or landing.
If the gear is still there maybe you can shift the empty_weight_CG_position forward.