I have pesonally jumped out of a R22 and heliduck is right, you don't actually jump of it you fall off it, and when you do miss then the pilot is generally pissing himself while the jumper is trying to fiqure out how many bones he has broken!!! You definatly can not be a fat bastard when you are up around 7-8000 ft doing this!!
Sasless is right in saying the ideal people would be midgets or dwarfs as they are small and light and you can fit two in the 22 at once!! they do roll alot faster though when they miss and find it rather hard to stop!! They are slightly disadvantaged if they do get on to a bigger animal though but generally they can climb on there backs and ride them like a horse!!
that would be laugh to watch!!!