Ever consider using gaffer tape?
Your post makes me wonder do people put their lenses in mount first or lens first.
I put them in lens first as all my bags have top opening for quick excess.
Since the mounts are facing up, I can change lenses without taking the lens completely out of my bag. Also, can do it on the move without stopping to lower the bag. If I lose my grip on the lens it drops back into its slot in the bag. Also, the raised cover can provide a little shelter from wind blown dust, sand etc.
