Interesting, however I would suggest the .75 (11bore) due to there being easily procured moulds (& wads) for this size.
The .715" Lyman mould would work very well with a 10 ounce denim patch, or, of course you could easily get a Tanner mound made at an even better price.
I personally have .710", .724" and .740" mould by Tanner moulds and they are are perfectly machined. Since their work is all custom work, any size you want
is doable.
If choosing a .690" bore size, then the .662" Lyman mould would work just fine, with the same 10 ounce denim patch.
Either would barely make a snug fit, but one that would shoot quite cleanly.