Our #2 was a tummy sleeper - as in would wake every couple of hours on his back and sleep through on his tummy.

Just follow all of the other SIDS recommendations - apparently one of the risks of tummy sleeping can be overheating, especially these days since many people have ducted heating.
So - good ventilation in the room, and definitely keep the heat down. Don't wrap bub, so he doesn't overheat and can get himself out of trouble if he needs - is he strong enough do you think?