The RS Gen 2 BEC can be programmed at either 6v or 7.2v but you need the Hotwire to do that program change (it comes set at 6v out of the box). This means that any servo is ok to use. Even Savox HV servos are totally fine with the Gen2 - no brown out issues.

My advice is the Savox 1256TG for 6v and the 1258TG for 7.2v. I have 1256's running on 7.2v without any problems as well. Both are digital high torque servos.