Be careful comparing yourself with top racers, most of whom are not much bigger than Jockeys. If, like me, you are 6'1" and 17 stone, you will almost always appear to be sitting further back on the bike. Bikes also make a big difference. On an R6 my backside is almost always flush against the back of the seat pad, but on the R1 it isn't. Different shaped tanks and seating positions. However, I almost never have my crotch against the tank. Think about how uncomfortable it feels and how hard it is to move around.
The trick is to get comfortable and stable on the bike. If you aren't the chances are that you will provide unneeded or incorrect inputs to the bike (such as stalling on the gas or inside bar pressure) which can help contribute to a low side. Either way, eating bitumen is a real bummer. How's the bike?
Cheers,
Isaac.
