I'm using PowerHD servos on my kits.
L-12HV - Digital, waterproof, all-aluminum casing, low-profile, coreless, titanium gears, high speed @0.06secs. $60 - installed on my FF03
LW-20MG - Digital. waterproof, aluminum/titanium gears, 20kg load. $22 - installed on my CC-01
Both servos are working great!