As a general rule, I'd wait at least 12 hours and if no progress, follow Sally Sunshine's guide to assisting a malpositioned chick. You'll have to use your best judgment about if the chick really does need help; if it isn't progressing at all or if the membrane looks dry are valid reasons to assist. With an early hatcher, though, it still may need time to absorb the yolk.
Personally, if I was worried about a chick, particularly a malpositioned chick, I'd assist it even if it ultimately didn't survive. Early on, I waited too long to assist and lost chicks that couldn't get out for one reason or another. I'm much more "hands on" now, but I try to give the chick every chance to get out on its own before I help out.