I want to be able to use it for some serious torquing, such as rebuilding struts or pressing out ball joints - the workbench has a 1 1/4" MDF top.

I am considering using a metal sandwich on top and bottom under the vice, but the heaviest metal I could come up with at Home Depot is 22 gauge - I bought enough to double up but would rather just use two plates of something heavier, especially if it's something I could scrounge rather than having to buy.

Any advice is welcome.

If I do use two layers of the 22 gauge, would it be better to bond them together with some JB weld?

 

We have two MDF benches with vices mounted to them, one small vice (4") and a bigger 6" one, both are mounted with just bolts and big washers on the bottom, when we clamp our ferrule crimping tool in the vice I wool "hook in" a 1-1/4" closed end wrench into the vice handle and lean all 230 pound of me on it to tighten it, and it's just 1" MDF, in 3 years all we have had to do is tighten the 3 bolts up a few times.
A plate on the top and bottom can't hurt but I don't think they are necessary. 94