This is about spot on. The lower denial island being where it is is screwing everything up.The main difference(I'm guessing from memory on sizes) is "normal" bucking bars are about 3/4" tall, OOW uses a denial island that is about 3/8" lower thus the need for a bar that will clear the lower denial island.
I had thought about doing that at one point, problem is my bar isn't narrow enough to fit between the island and LSP. So I couldn't use an extra piece if I wanted to.I have done OOW side plates with my normal bucking bar and just put a piece of 1/8 x 1/2 flat over the rivets. You can get the flat at almost any hardware.
Brad - Big44maghunter