Using blocks under automatic levelers

Well, thanks for all your input. Sounds like it's best to scrap the 2 layers of 2x10's since splitting is an issue. I like the idea of 4x4's sandwiched with 3/4" plywood. And I suppose there is really no reason to even extend the jacks on my level, gravel pad. But having the blocks handy while traveling might be the best idea.

Thanks again, everyone!