Thanks for the info guys
I think my plans evolved a bit since posting this to where I could theoretically and with *relative* ease make custom build silicone fins for a person's actual foot instead of generic sizes :P If I did go that rout my plan was to use either 40-60A short hardness stuff for the monofin itself and reinforce it with powermesh & perhaps some dragon skin on the outside since it's the most durable of all the silicones available.