Quick ass eating question! [NSFW?]

Hey guys,So, my boyfriend and I have been together for a while now (1.5 years), and even though I'm a bottom, I'm trying to get into topping because it's something I've always wanted to try. My boyfriend has always been a top, and is willing, although wary, to give bottoming a shot. There's just a small snag.I really love to eat ass: it's fun and easy. However, my boyfriends ass is a little on the heavy side, and I find it difficult to eat him out properly. I don't have the longest tongue in the world, and the way his ass cheeks cover his hole makes the whole thing harder. Licking the rim isn't hard, but I just can't get my tongue inside to really make it pleasurable.Do y'all have any advice on how to get around this? Positions, techniques, idc, anything is appreciated!