Thanks guys.
I'm using 2" for this experiment, and they have a 1" square on them. I haven't tightened it down, not quite- I can't with just my hand, which makes it less desirable for this purpose.
Maybe I should put a pair of small channel locks and a decent modular screwdriver in BOB....
Why is it every time I get a good idea, I want to put more weight in BOB?