I think a lot of people run 5.5 in 4wd but those things are easy super easy to drive. You should ask at the track you are going to race at what most of the fast guys use. That would give you a good idea of how much power the track can take. Looking at videos these days it seems to me not many of the top racers are using full power very often around the track so I don't think a slower motor is any real disadvantage, a crash each 2 laps costs a lot more time than being .02 of a second slower down the straight
. In the old days you could race 27 turn stock and just hold it flat almost everywhere but those days are gone
. You know that I have only a 3000kv motor in my Madrat and it's not exactly easy to drive:0 at least not on dirt, I imagine carpet/astro turf in the UK is a lot easier but it's not really fast enough to race either. So even a 8 turn I imagine will take along to to master