I struggle with shorts too. I am short and curvy with a big behind and large thighs, and shorter shorts (3" inseam) just don't cover my rear end all the way! It seems like the only other choice is bermuda length. I don't often find shorts with 5" inseams, which I think would be perfect for me.
I did happen upon these from Free People and am loving them. In fact, I have them on today! You could hack them off to whatever length you like. I had the raw edge topstitched so it doesn't continue to fray, and I fold up the bottoms to make it look like the shorts are cuffed. On me, the leg opening is snug on my thigh, not loose like on the model.