Ignoring fit issues at the back for a second, just to check are you running the light saddles packs forward? Assuming so it must mean your car is Much lighter than anyone else and have significantly different weight transfer even if static balance is the same. I think this is why you might have less drive than anyone else? The stock layout isn't broken
Also, I used to have a perception that in lower grip conditions I had less drive, but actually when I tried others cars at the ends of meetings I found this wasn't the case and I was psyching myself out. I did however have better, safer on turn in.
Ref the fit issue, I have mine with low gearbox and not external limiters and it JUST touches the angled driveshaft pin if I push the suspension up by hand. I have run a little tranny height and not changed anything though with no sign of any ill effect. I would just swap the Losi bearing spacer out and shim the driveshafts across if I could ever be concerned by it.