Revised canopy SW? What u mean?
Anyway what I know about possibly AH relevant K4 differences is:
Faster due to gear doors and tail wheel.
A bit heavier due to above.
Was a bit less stable at 30,000feet than G10 for some reason, according to the pilots.
Had internal components relocated to improve balance.
Most important it had new ailerons with flettner tabs. These helped increse high speed rollrate and eased pilot effort in rolling.
Basically flettner tabs are small tabs that automatically move in the opposite direction of the control surface.
For example Lets say:
The aileron delects up.
The flettner tab automatically deflects down.
This acts very much as a small wing flap, increasing the lift and helping keep the ailron deflected up at high speeds.
This is what would cause the incresed hig speed roll rate.
Apparently these flettner tabs were very effective as some early A6M Zeros had them fitted. These planes would then rip their wings off from the increased roll rate.

As for where I heard pyro said he didnt want to do a K4, it was in an old old old thread on the BBS.
Maybe now he has changed his mind, I donno.
