u/Terrible-Bath

Hi all,
Sorry if this has been posted before. My 11yo seems to be settling into GK as his position. But he goes 100% on his dives in practice and his sides/hips are getting destroyed with turf burn. He had club tryouts yesterday and he couldn’t sleep last night because his side was so painful.
He wears low profile Adidas padded shorts. He finds the Storelli stuff too bulky. But, this is the side area above shorts anyway so padded shorts don’t help much.
It sounds dumb but I got him a wrestling singlet but no luck on getting him to wear it.
Any advice? Or is this just part of being a GK?