Ways to check legs for narrowness and pinched hips?

[Tale of Tails Rabbitry]

@Bunnylady I have "resistant" buns to that whole draw up the legs thing. I played with posing three 9-week olds for an hour yesterday and only one would draw up her legs briefly when I was rolling her back, but I will try this way again today. I do know that two are weak in the loin, one more so than the other, when running my hand over the top line down to the backend, and one is pretty good, I think. So, there should be no pinch (hand, not rabbit) as I run my C-shaped hand position down the backend anywhere in the leg areas before dropping completely to the floor? Otherwise it is undercut or something else?