Right, Bringing everyone back up to date with this!
I ran the car for the first time in anger at Kidderminster 2wd regional recently, and all I can say is that I was letting the thing down!
It was hugely stable over the bumps, despite only being 10g above the 2wd limit (with about 50g lead added it comes in at about 1485g/1490g depending upon tyres, lipo etc). The speed could do with coming up a little, but not running 5 year old TrackPower 3200 saddles might fix that!
Despite this being the first real race (only done a smelly nitro meeting, one club night and the Oswestry GP in 3 years) I was able to put in some consistent lap times with the car, and not once did it try to pick up the front wheels, despite the grip being huge!
OK, so the bad points:
1 - Not enough Toe-in at the rear - So couldn't get the power down quite as hard as I'd have liked.
The design of the chassis is the limiting factor here, as I can't use different toe blocks from the standard car. I need to either use a rear outboard toe-in hub (any ideas here?), or find some other mounting blocks (I have a plan there, involves a bit more dremel work though!).
2 - Lack of adjustment on Top shock mounting holes.
Because I'm using the wing mounting holes on the original MX4 shock tower, I've only got one mounting hole for the top of the shocks. Not toooo big an issue really, I can just drill some more, can't really do it trackside though!
3 - Yokomo Diff Sydrome
As any one who has owned either a YZ-10 or MX4 can tell you, the diff screw coming undone is a right royal pain. Need to find a way to fix this permanently, as cleaning then using superglue clearly isn't ideal!
4 - Rear track too narrow
Easy fix this one, I just need to get hold of some thicker drive hexes. (probably got some in the loft on an old car!)
Overall am really pleased with it, certainly didn't drive like a home build abortion, it was actually really drivable and felt like there was much more to come out of it.
Anyway, not sure when it'll next come out, but will hopefully have these bits done to try it again.
edit to add - Neil caught it on camera! only one pic, but it's the furthest right in his reel of pics from Kiddy, at 3:47 in the vid!
http://www.youtube.com/watch?v=X8BSP8fc6s4