I was lazy and just went with BenchCrafted. It allowed me to concentrate on the wood part of the vise. Mine ended up being a 'jig'. I couldn't decide on whether I wanted to do a table behind the fixed chop, a camfer on the moving, if a camfer what angle, etc. So I built mine from hard maple, more or less on the BC plan but with the York vise shoulders, and added threaded inserts to the back of the fixed, and top of both chops.
So now if I want some new feature I build a widget and screw it on with 1/4-20. That's a great idea, except there are always new widget ideas, and they end up taking up time and attention. I tried the springs idea to spread the chops, but found them more trouble than they are worth - it really doesn't take much to move the chops. If I do it over again, I would build a smaller one. It would be in addition to the standard BC large size, but that would simply because of the weight and space it takes up on the bench which ends up seeming like a silly reason to do another one. I will eventually buy longer rods from McMaster, probably already should have.