I've only had 1 chick could take it full doggy, but that still was a stretch (sorry lol) sometimes... The laying-doggy is the best for that, plus, you can short-stroke just the lips with your head or 1/2 way, while giving her a serious reach-around, or pull on her tits; any other sensation to distract her, while you ease it in, while she's "warming up" and beginning to relax her pussy... I can't wait, soon I'm going to do this to my chick and report back ;-)
Oh, also, you could try "sideways-doggy" basically she's in the spoon position, while you're perpendicular and entering her from the back side. This really helps if you've got serious girth, bc the vagina opening is wider going from anus to clit, vs side wall to side... It won't help if you're very long, but girth is usually the issue.
BTW- What is your length x width; since you said "very large?"