I could wel be wrong on this one, but I'm sure I read a bit on here that someone said the 4WD losi shocks were longer than the 2WD ones , might be why your getting so close to the limit, surely it wouldn't hurt to put a spacer in to limit the down travel, your still going to have more than with the standard Schumacher ones.
What mounts did you use at the top? Standard Losi ones? Haven't got round to trying them on mine yet because mine got a bit smashed up when someone pulled out across the straight infront of me when I was at top speed
unfortunately bent up all of the screws that hold the wishbones and then to ad insult to injury they sheared flush with the gearbox when I tried to take them out!