Trailboss and Red Dot give you almost exactly the same peak pressure for a given velocity. The old standby Bullseye is a bit lower. I still have half a can of TB left from a trial in a normally super-accurate 9" Colt Officers Model. Accuracy was abysmal, vs. my usual Bullseye load. Maybe it's better in bigger cases? Nope. .32-40 single shot rifle, same-same. And by weight you have to load about 35% more TB, vs. Red Dot. Not economical.
All that said, if Bubba just HAS to load smokeless in his ROA, let it be Trailboss. He'll at least be prevented from double charging.
Could you press sleeves into the ROA cylinder to reduce the powder space?
I'd set up the ROA chamber as a cartridge case in Quickload, but too sleepy tonight. Not sure I'd want to publish any data anyway. Anybody else with QL and a ROA care to risk it?