I recall reading something recently (past year) that stated most all the r/c manufacturers do test flight packs and servos for 6V operation due to the popularity of 5 cell rx packs- even if the r/c packages don't state such- it is generally acceptable to use 5 cell packs in todays modern r/c installations- the RX and servos can take the extra 1.2 volts.....

I recall reading one of the reasons r/c manufactureres don't openly endorse 6 volt systems is the general propensity for people to want "more" and therefore try 6 cell r/c packs- that along with sticking to the "Manufacturer's Recommended " voltage of 4.8v keeps r/c equippment well in the safe zone and keeping repair centers doing work on "actual" useable voltage problems, should they surface.

Sorry for getting sidetracked on the regulator query.