[Fenrir]

Because Tihi, you don't know what you are talking about and someone threw you a bone to shut you up.

I'm a Spit flyer. So no lufty bias here.

What was fixed in 4.101 was an aileron trim issue, nothing to do with stability.

As for your perceived instability - I've been flying the 4.10 & 4.101 spits for a month now, I see a very low trim elevator neutral trim speed, which I find questionable (but having been shown the source of that by TD I cannot argue because I have no data with which to counter) but there is NO behavior AT ALL which indicates pitch instability. The a/c does NOT tighten up in turns, does NOT hunt whilst flying straight and level and can be trimmed quite easily to fly hands off.

As the aerodynamically understood principles of instability go the 4.10/4.101 Spits are paragons of stable aircraft.

If however you are referring to the adverse yaw, this has been discussed. Try applying a little rudder with the direction of aileron - this is called a coordinated turn - and your problem should go away; after some practice, naturally.