I would say 5% is as high as you want to go, but I think 2% is generally accepted. It also depends on what kind of player you are, do you cash 1/3 but lots of mincashes, 1/10 but go deep when you do...as to what kind of downswings are likely. You want your risk of ruin to be very low, but don't want to impede growth by being too much of BR nit.