I think some responsibility also sits with HPI, the Savage Flux manual and all the advertising literature pretty much invites you to throw a 25t pinion on it and run 6s. Even on the stock 20t pinion, that's a horribly overgeared combination for the Savage Flux.
20/44 is fine, even optimal for 4s, but 6s? I'd be running 15/44 and watching my temps like a hawk!