Doggy always worked well for me and my chubs of an ex. ;D (I ♥ him even if he's my ex.)
Missionary is good, but proves to wear a bigger, out of shape person out quicker.
But if you want positions... (LINK
.) Just as an FYI, that site is so not work friendly.
It's got like, computer-generated models that show the different positions. There's TONS of them. I'm sure you'd be able to find something that works :)