JasonB: Think I ended up going with the stock foams as the HPI firm foams were a little bit too err firm when mounting on the inner bead.
My truck is XL length and that tends to highlight traction issues. With standard length it will put the front wheels up easier but you need much more traction with an XL length to do that. The GT2 tires were great for power drifts on flat dirt but once I threw on some old GT tires (mounted again on inner bead) it was a night and day thing. Much quicker off the mark and easier to get the front wheels in the air when i wanted to.
thezero: I would like to try Trenchers one day but I'm guessing i would have to gear really low as the weight somewhere around 400gm with wheel from memory. Also not that keen on putting that kinda stress on the drivetrain.