My moki is well broken in 15+ gal. 7100 is a bit slow. I get more than 9000 on a MA 18x10 Scimitar. It should get at least 8200 on the wide blade I would think. I am using 5% Moki blend-15% oil I believe. You can probably go with the lower oil fuel and get more power after 2 gallons have run through it.
FYI, I would not buy a Moki 1.8 new now that the OS 160 has come out. I'm getting the same power from my new 160 (5 tanks through it) and it is easier to tune and rock solid reliable with a pump on it. I have more time on it than 5 tanks but it hasn't changed since.