I went and looked up the Bean’s girdle and man that is a very nice looking piece. I like their o ring grooves to seal it to the block and as for the aluminum part, their argument that a girdle has tensile forces on it and that their thicker material makes up for its lesser strength sounds reasonable, although I have not punched any numbers on this to verify.
Here is my immediate concern though: the 12mm mains. To me, if you are building an engine where you need a hardcore girdle like that, you’re going to want to do the 14mm mains also. I can’t find the info on the ones that do not come with the studs if they offer them with larger holes and dowels or what. Anyway, this is just a thought