Exactly what Mike said.
I was intending to find Sherman Bell's article to refer to before posting, but my time is not my own at the moment. Forgot about Wrighty's reference.
Douglas: as I indicated in PM the light "practice" loads are fine in a single-barrel as there is no requirement for regulation as in a double.
With normal medium-burning powders just work up to your tolerance limit or ballistic requisite and add filler/wads to keep the powder at the business end.
Trail Boss is an entirely different kettle of fish however.

I'm sure that all else being equal you should get not just reliable extraction but ejection with the 2 3/4 case in the Martini action. I wouldn't be so quick to write it off as an African safari hammer.