Ok I just double-checked my 8E racks, and it refreshed my memory. The support bracket is not necessary. I believe that it provided no benefit after the TU56 was mounted... it was merely present in order to make it even possible for one person to bolt the tu56 to the uprights. It is a non-trivial amount of weight, so holding it in place while bolting it in is tenuous at the least and most likely impossible. The support bracket just provides a front edge to help hold it up during installation.
Being a stickler for authenticity, I was looking for that support bracket but never did find one. So... I wound up using one of those horizontal bars/plates that were commonly (DEC provided) mounted above and below a stack of lead counterweights, as it's mechanically almost identical and provides exactly the same benefit in the same spot. I left it installed, in case I ever wanted to move the TU56. All this occurred in the short version of the H960 (I forget... H962? The one with the sloped front). The sloped front at the top was just the tiniest fraction too far out to allow the TU56 deck to tilt down - despite the fact that DEC obviously took pains to make it require no clearance overhead. Since you're using a full height H960 with a different nameplate piece at the top... it may just work fine. But given the weight, I'd not try it "just to see" ;) YMMV J
