I have several pairs of SPD-SL pedals I need to move if you're interested.
Gotta put up an ad.
I used them for 5-6 years but increasingly get numbness problems with road shoes but not MTB shoes. I don't think SPD-SL is any part of the problem, more the stiffer road soles + the curve in the sole that forces your toes up.
I think I have 2 pairs of the Ultegras.. one metal body, one carbon body. The carbon ones have super minimal wear. I got them last September and gave up on them in a couple hundred miles. (Fitter tried to tell me the updated design on the carbon ones was going to solve my numbness issue... nope nope nope.)
If I could find a road shoe with a flatter last it'd probably do the trick.. not easy to find though. I ride flat/heels down and the shoes all look like they are built for toe-pointers.