[RC-Monster Mike]

I don't know that you can really call 10mm the "established standard" on 1/5 electric. I don't honestly think there is such a thing as a 1/5 electric "established standard" to be honest. It isn't as if there has been some booming electric 1/5 market for the last X years. I suspect the Castle system will establish the standard, as there simply isn't any other 1/5 systems in existence as far as I know? Sure, people have used some expensive HV ESCs and large motors intended for the boats or planes initially(myself included), but in terms of a dedicated system, Castle is the first and therefore will be the established standard. On a similar note, I have a full range of 8mm bore mod 1.5 pinions - not sure if such a source exists for 10mm bore pinions(and this would also limit the available size at the small end as well). It is also far easier to make a 10mm to 8mm bore reducer once for all your pinions than it is to ream out all the hardened pinions to 10mm.