Update: I went back with some tools to try out a few things. The resulting setup can be seen below.
The things I tried and kept:
- 25 Deg. caster: Increased steering (but also made the rear end yet slightly looser off-power), more importantly it made the car feel much smoother.
- 3 Deg. anti-squat: Seemed to add a little on-power steering.
- Rear shock more upright (middle top hole): More initial on-power steering, rear end can be kicked out to make a tighter initial turn. Rear however starts gripping again once the car starts rolling, ending up with (nearly) the same on-power understeer in long turns under power.
- Looser slipper: Made the car less edgy, but didn't add steering.
- Reducing rear droop back to kit level: This did a lot! Off-power the car became calm and stable, on-power the car had better steering in general, high throttle was less affected though than medium throttle.
- Longer front link: The car seemed to get slightly more steering in general, but off-power stability was kept.
- Swapping 24g battery stopper from rear to front end: Increase in steering on- and off-power, front end is more planted, the rear end is visibly slightly looser but in a controllable way.
- Front rollcenter, 1mm lower inside ball stud: The car seemed to have slightly more steering and have a smaller turning radius, yet didn't feel more agressive.
Things I tried but reverted:
- Schumacher Minipins, Yellow (4WD front & wide rear): The car became quite vicious with the car sliding out off-power. On-power steering was good for medium throttle, but understeer came back at high throttle levels. I reverted back to the dBoots setup (as I didn't have cut staggers with me).
- Rear rollcenter, 2mm higher inside ball stud: The car became slightly looser at the rear, helping steering, but I reverted this because I'm afraid the rear end may become loose on the low grip (PVC and Wood) sections of the track.
This is as much as I could have tested on a patch of carpet that was about only 4x8 metres
The rest I'll probably have to find out on Sunday. The car feels better already: The off-power oversteer is not there anymore unless you decide to brake into the corner
The on-power understeer is still there at higher speeds but is now manageable.
So despite the steps, I bet there's further improvements to make. If anyone has suggestions what could further reduce on-power understeer, your suggestions are more than welcome!