J2M5 feels heavier to control than J2M3

I’ve been a tad puzzled over the J2M5. On paper, it seems to be very similar to the J2M3, excepted it’s a tad bit heavier, and has an engine (that per the game datacard is lighter than the J2M3’s, so not sure where the extra weight went) made for high altitude.

But when I fly it, the controls feel strangely heavy, like it’s a pain to get the nose pointing where you want. Now, J2Ms are not exactly meant to be A6Ms in the first place, and they’re known for the controls getting heavier in dives, but what I’m saying is, next to its two sisters (haven’t tested the premium J2Ms, so can’t speak for them) the J2M5’s feel comparatively notably heavier to steer, more or less at all speeds, and I’m not seeing anywhere a reason that could explain that - from everything I can see, it should handle relatively similarly.

So I’m wondering if I missed something, a detail about the J2M5 that could explain this feeling ? Or if the feeling itself is just weird. And as an aside, I’m also curious where the extra 70kg (per the wiki I think) are, maybe it’s related, and according to the game it’s not the engine, so I’m not sure…