They're an awesome servo! But the same price ($99 Amain) you can get the Hitec HS-7954SH instead. Basically the same servo with the same 333oz @ 6.0v rating but is rated for 7.4v with over 400oz! I run a HSR-5980TG which has the 7955's titanium gears but is HV capable with the same ratings as the 7954 and a slightly different case. I run that sucker in a LST XXL without a servo saver and it takes anything I throw at it.

Running an external BEC is a must to get the most out of a servo. I've tested servos for amp draw and saw average draw around .75amp with spikes over. 1amp. I went from an internal esc Bec rated at 5amps to the 10amp Castle ( set to 6.0v) and saw a very noticeable performance increase that was well worth the price and effort. Things only got better when I set it to 7.4v!