Tony, the 'L' is pretty darn stiff. It's got a long slot in it, which is for exact placement fore-aft. Bigger riders might want to get the placement figured, and then add a t-nut to keep it from shifting around. I pushed Adam's around first time out, but added a thin piece of sticky-backed rubber under it, and it not moving now (but I only weigh in at 170 or so).
The curvature of the toestop might not work with size 11 +Up shoes, but may be bent to straighter arc using a vise, maybe a bit of heat... It fits really well with size 9's, totally holds the shoe without curling the toes any. My only 'real' concern is sharp metal edges, so, just don't Fall on it!
This is a really nice, light, easy to set-up Toeblock, one of the best feeling/working units I've seen.