Hello everyone again!
I think I've just found a Spitfire FM issue.
Nearly all of IXc Spitfires: both F. models, Mk.IXc, and L.F.Mk.IXc with clipped-wings have a mass of about 3390 kg (3387.54 to be exact).
However, L.F.Mk.IXc with non-clipped wings is 118kg lighter, which looks quite illogical compared to the planes with the same airframe I listed above; besides, that gives him a climbrate of ~26 m/s at sealevel. I guess that'd be a little too much even for this great airplane. Hope it'll be fixed
EDIT: Just looked through other new spits: it seems that L.F.Mk.IXe-25Lbs-CW has a similar bug. It weighs 3270kg only, while L.F.Mk.IXe-18Lbs-CW has a mass of 3440kg - 170kg difference between two differently boosted planes which are identical in all other aspects.