Hi Chris, someone else may correct me, but in my (racing) experience, above 640cc (for the srx) tends to be a hand grenade waiting to go off!
More or less anything bigger than std. is generally going to be (on average) less reliable, (in my opinion)
Having said that! I, myself, ran a tuned srx620cc on the race track for about 12 years, & never had the engine apart!
Other opinions will differ from mine I'm sure! but that's my twopence worth...........