I've gotten some great advice and I now need to try a few things.
One poster said that I need to make sure the front and back are level - that perhaps I've pulled the front up too high. I need to try the muslin on again, keeping everything level and take some photos from front, back AND sides.
Another poster has given me the idea of using the WB the way it is and using elastic as a kind of interfacing. If I don't attach it - just enclose it in the WB, then I can shorten it as I lose size. Great idea - and I think I'll do this, but so I need to get the pants fitting first? Maybe I need to cut out a WB, recut the top of these shorts according to the pattern and sew it together as it's meant to be in the pattern.
Yet another poster mentioned crotch length...apparently, the pattern should measure my crotch length plus an extra 1" for ease. I've measured my CL - it's 29.5". Next step is to measure the pattern and see if that works out.
Finally, I'm also going to try molding my crotch line with tinfoil and getting a template happening. There are a few threads on PR about doing this and it sounds interesting, so I'm going to give it a go.