Women's shorts (especially large sizes) have extra butt room. I normally wear a men's XXL for men's bike shorts, but women's shorts I wear a XL and they have a nice rise in the back! This was confirmed by my mom who has a woman's XL is a man's XXL.
The only thing you have to watch out for is A they are a bit shorter inseam generally, and B make sure the stitching is not going to bother you junk.