What is the best position in your opinion with a fat girl?
-Whale Wang Willy
All of them, duh. If you're having actual trouble in your fattyfucking pursuits, this is pretty much the best guide extant. Don't be discouraged or embarrassed by everything in the way, ladies and germs; half the fun is all that shuffling around. Just take your time and don't be stabby you're when poking around. Don't be afraid to use pillows if you have to. Depending on the lady's size and shape (and yours), you may not be able to do everything. But you can do more than you think. Find out what works for you and don't get frustrated if that takes a bit.
Me personally, I'm especially fond of girl on top, spooning, and reverse cowgirl. Doggy just barely misses the first tier. I've developed a serious affinity for 69ing. Girl on top, me underneath, warm belly pressing down on me with her ass in my face and my paws around her breasts or stomach or thighs while we suck each other to blastoff? Competing to see who can make it harder for the other to concentrate? Yes, please.