Leave it to me to find the exception. lol.
The Veco 19BB is a *great* engine, one of the very few that can come close to a modern 20. I think you could find a much better use for it, like a Skyray 35, which will be generally a much better airplane overall.
But I note that it is the super-hot-rod of its day, and it still can't match a low-ball economy engine from the 90s, the OS-20FP ABC, and engine once commonly available for a mere $47. There are much, much more powerful 20s used for RC cars, Picco, other OS car/"buggy" engines, and many 15s that are much more powerful than a Veco 19BB.
I would guess the Akromaster kit came out in the late 60's/early 70's, when a Max III 15 was a typical engine for it. That's the problem with specifying it by engine size, a "15" could mean anything from a Enya 15 baffle-piston engine not much stronger than a Tee Dee 049 to a Fora 15 F2D engine that is putting out more actual power than a piped PA 75 in a typical stunt application.
So, I think you might have some problem keeping the speed in check. I have flown a full-size Ringmaster (370 square inches) with a Veco 19bb/10-5, the first flight was something around 3.0 seconds a lap on 60 foot lines. The wings were probably pulling in 3-4 inches of dihedral in the round loops, or at least for the short periods I saw the airplane well enough to tell. We got a 10-4 for the second flight, that bumped it down to about 3.5. Similar results with the "20-point" Ringmaster, which is the box art picture for the RSM Ringmaster kit, 4.2 seconds a lap with a 9-4 APC. We switched to a 20FP, same prop - and it went down to 3.8 seconds/lap.
Brett