E-maxx 3905 driveline

[GT35R]

I've recently been testing a fairly new 3905 on a 6S setup in preparation
for the MMM to arrive and am having problems with the centre rear driveshaft.

Firstly, I don't have reverse so there is no jamming it from back to forward etc. And so far I haven't even jumped the thing.
But both times I have driven it offroad (gravel then sand) the plastic centre splined driveshaft lasted less than 3min. It just twists out the holes where the universal joint is at the back. I repaired it like new by grinding down and making new holes but it did the same thing again.
Also the drive yoke became sloppy on the pinion output shaft which had to be spaced with a washer so the R&P wouldn't strip.

Anyway, what I did notice both times was that the metal UJ was too hot to touch! I'm wondering if the failures are due to the friction of the UJ heating and softening the surrounding plastics.

I want this thing not to break, I will not abuse it, just want it to handle the power. Its only geared for around 35Mph so isnt more extreme than a typical 4S setup I imagine.

Sooo.. will switching to those metal centre CVD's cure this problem? Have people found them to be the only driveline upgrade required for BL power, or will the 4 wheel driveshafts need doing as well??

Any advise will be appreciated, thanks.