Hi Bill, I suppose the 2x4 are overkill, but they are readily available at low cost. Upon rereading my first post, I see I typed 12' for length of gusset, hopefully obvious I meant 12". As far as overkill goes, I also used 3/4 ply for my subroadbed. I wouldn't have if I had had to buy it, but a large quantity was available for free. For free, even vinegar is sweet, as they say. Yes, I can, and have, knelt on my benchwork and am glad I built it as I did. I also space supports 24" when required with no problem, even in my rather humid basement.
Gary