10.000 is not too good to be true,,
G26, Mejzlik 18-6, Abell muffler, 8800-9000, 17 lbs measured thrust..Verified by several owners...Piped, 10,000 rpm, didn't measure, The very accurate Grish Brothers chart says 22 lbs....
Dick Hanson gets the same performance with his Roto 25, all you gotta do is read some of the posts in this forum...
The chart shows 13 lbs at 8000, very close to your assumption...
the G26 turns 8200 with the stock muffler, which would be 13+...