I don't think you'll gain anything on the 8s, as they say to limit the motor to under 1200kv at those voltages. Playing around on a spreadsheet I built to determine speed, puts it at 23 mph with the 12T pinion. A 22T pinion would put it about 40 mph with final drive ratio 9.77:1. How well do motors in that kv range handle getting geared up like that? I think it would make a mean truck puller, though. lol.
?2050×14.8v= 30,340rpm.
1200×29.6v= 35,520rpm
With stock pinion it would be faster than the stock motor on 4s. I thought it did over 30mph stock on 4s.