Any volt meter is fine, and as someone mentioned, putting a Volt-Watch meter on the plane itself is a good investment, it will give you real-time readings of voltage, not actual numbers, but LED's that display from good to marginal on a scale. I know all about the tank hieght issues in a pluse, I had mine where it was hard to tune due to the hieght of the tank, but when it sit's on the ground, the tail is lower, and so is the tank being the fuselage is slanted downward. I would refer to the owners guide for the engine and verify the needle settings are correct before pointing to the tank being high, to hydrolock the engine it means that it's drawing too much fuel in the first place. As far as the servos, yes digital servos draw more power, but yours are mainly standard servos. Personally, I prefer std servos due to the power consumption, nothing I do requires high percision outputs on the control surfaces. So with that being said, as long as your battery on standard servos gets about 3 hours minimum runtime till it hits 3.8 volts, then your OK. but if after an hour you find the battery at that point, start thinking about replacing the pack with a new one. This is providing that there is no binding in the linkages or servos that are buzzing from being overloaded or bad potentiometers. There is always a reason why something is happening, it's up to you to put the pieces of the puzzle together and make sense of it all. I do this daily for work, I gather little tid-bits of customer information and piece together what happened to come to a conclusion of wat or where the problem is. Trust me, being a detective sometimes stinks, but the littlest thing can make a big difference, like someone not setting the needle correctly at the factory.
