I'm not sure why this didn't dawn on me before.
The biggest problem I've seen with trail runners is that the lighter you go, the more flimsy they are. The rock plate might not be thick enough to prevent damage to your foot.
So my idea is to bring a 2×2 inch rock into the store.
Then you can just put the rock on the floor and step on it. If it hurts you or you can feel it poking into your feet, then obviously repeated impacts are going to injure your foot.
Shoes are a VERY subjective experience but this is a pretty objection selection criteria.

