Ludwig-Heggen, I know your problem same way you do. This is a MAJOR bug in my eyes. It is unacceptable to use long arms to solve the problem. Servo gear will be beaten hard, and any slop will become magnified.
My way around the bug = I quit using normpos for or aft, one simply must be able to get full travel, so only option is to use in "MITTE".
To end in the case that when my stick is neutral, the flaps are both deployed (ausgefaren unten) already halfway, say 45°or so. The servo is unaware of this, it thinks it's in neutral, so it has still 50% each way to go. But the servo arm is also (like the flaps) on 45° repositioned (taking arm off and puting it at 45° back on).Make sure they both flaps are same amount down, if nessessary adjust one of the 2 servo-neutrals so the flaps match up with each other nicely, seen from outside the glider, looking from the back. So stick neutral = servo (in his own world) is neutral = flaps and mechanics are already in 45° position. Now you have 50% left for going full flap, and 50% left for retracting to clean airfoil (or even more for reflexing the flaps).
In your case, stick down means no flap, play with stick-travel amount & servo amount to make it so. Have some spare on the servo trow, so it can move UP for reflex if needed.
Same for stick forward, play with stick-travel & servo amount so the both flaps go same down completely as much as you want.
One issue remains: if you want to change the "no flap deflection position" setting, meaning wing is clean profile, and you have some servo drift to correct, you cannot do this anymore in menu NEUTRAL, stay away there because that's only for the 45° situation correction. If your flap is not in-line with wing profile anymore (servo drift) when flaps retracted, then you now must correct that in the servo-amount menu.
Of course this has some complications for ailerons if you want to make butterfly function, but you solve this by setting the aileron servo neutral (servo neutral menu) at 50% or -50% according to your build situation. So like the flaps (halfway DOWN), also the ailerons are halfway UP (from full crow) when the spoiler stick is in neutral position.
So in my case both flap servo's have a neutral (menu) value of around 0, and both aileron servo's around 50% (+ or -).
This way I could do all F3J needed features to work, but with improvisating in the program section, no long arms.
I think P4000 has not this problem, but never had one, so don't know for sure.
Hope you can imagine what I mean, my german is too bad
Cheers, Jurgen.
