A little prototyping progress...
Cardboard TVPs with cut outs and batteries:
I need some sort of end stop on both sides of the dogbone. There must be a U profile with the right dimensions somewhere!
Servo can sit in its normal spot (more or less):
Battery placement in relation to the dogbone (vertically):
Ive got 1cm of 3mm thick alu on the bottom side of the TVP cut out at each end of the battery as it is. I wonder if its safe to go even lower? Damn I should have taken the 5mm TVPs!

If I could go lower it would help servo mounting... still for my friends inrunner project we need a different servo placement anyway. Bright ideas are welcome :)