KevinMc wrote:I'd also like to overhaul the ballast system and switch to a hybrid piston/snort ballast arrangement.
Using twin piston tanks either side of the ballast tank endcaps, or a single tank? I found some super little planetary geared motors on ebay. They're 3 volt motors, servo sized and operate fine on 5 volts from the receiver supply. If you run piston trim tanks from the regulated 5 volt supply, they're independent of the propulsion voltage, and you can use standard servo electronics to control the motors and piston position.