Ah jsloan notes, OS may, at their option, choose to defer to the United allowance because UA is operating the overwater segment. Per DoT rules, they may only do this if the UA allowance is as least as generous as the OS allowance. Note that none of the calculations account for your status on any airline - you would still be getting the statusless UA allowance on SOF-LAX (which is the same as the OS allowance in both cabins so it's kind of moot). At an OS counter, the OS elite waivers apply - namely, one additional piece for being *G.

I do agree, however, that the deferral makes it much more likely that the Business allowance will be applied since the MSC segment is now in business class. In that case, your allowance becomes 3x32kg (2x for the cabin and 1x for *G)