Dom,
Trekker runs an S1 Cat round EPR and is scary quick with it - or should that just be plain scary
Seriously, you won't be disappointed with an S1 - the Carbon is nice but is more expensive to replace when you break things - check out Racer magazine this month for the low-down on the S1 Cat - for the money it is impressive (and so is the CAT for that matter
).
As and when you get one - we can sort you a killer set up for EPR
As for weak points - much was originally written about the diff outdrives but the new ones should cure the breakages that was happening at full uptravel.
You'll get through a fair few rear bumpers at EPR with the transition into the concrete raceway corner.
Other than that - some Nortech whitey o-rings will smooth out the shocks and you can get separate suspension hanger screws from Nor-tech at the same time - I've not bent a standard one yet but I fear than I've not been trying hard enough.
Like anything - hit something hard and it will break.
Spur gears have been known to strip - especially with badly meshing and/or narrow pinions. A slight mod could see associated B4 spurs fitting on the layshaft if required.
The S1 (like the carbon ones) is permanent 4WD - many people like the option of the one-way layshaft roller.
Too much to write here before you fall asleep reading it.
Buy the mag, buy the car and get on down to EPR - we'll help sort it from there.
I'm sure if I've missed anything, Chris Long or others can chip in and fill in the gaps.
Good luck.