Ok guys...I just got back in from a proper run, after disabling Punch Control and tightening up the diff.
WOW.
I have it geared for just over 60mph according to Brian's calc, and after about 20 mins of moderate bashing about, the motor only just scraped 100F! She's got all the power you'd expect from this setup, but in such a relatively light truck, the motor really does throw it around. Wheelies at any speed, and no drivetrain issues whatsoever. She even took a couple of nasty tumbles with no problems; which is just why I chose the Havoc.
What really surprised me, though, is just how driveable the truck is. Being RWD, I was expecting it to be sketchy...but far from it. On tarmac and grass, it launches controllably and predictably, and braking is also drama-free. Cornering was brilliant; it almost felt like a 4WD, until you hit the gravel. The V1 Monster presented no problems whatsover either; it was pretty smooth, and braking was exceptional as I already said. I couldn't get a temp on it, but it can't have been stressed in this setup. I didn't temp the Elite LiPo, but I did touch it once; it was just about luke-warm. I'd say around 70-80F.
Top speed was the thick-end of fast, too; must've been close on 50-60mph. I did get a (fairly naff) video which I'll upload to YouTube sometime soon, but I LOVE this thing!
Thanks for all your interest and advice on this thing guys, I really appreciate it.