RE: Can you destroy a receiver?
Can higher than rated voltages destroy a receiver or servo? Sure. Will it? That depends, on the particular receiver and servo, some are just more 'sensitive' to abuse than others. A 7.2 volt battery is a fairly common size, find them in lots of things. And while it's always good to either over estimate, or under estimate 'things' to be on the safe side, it's also fairly common to use this voltage for powering R/C electronics. I've used a 7.2 volt battery for models with no problems. Not having had any problems using them, I also haven't done much checking of spec sheets, so my 'good luck' is more of a 'dumb luck' thingy than anything else, I wouldn't particularly recommend it. I can only say I haven't had any problems -yet- (and with my luck, the next time I connect one, all the smoke will come out of the electric stuff).
There is almost always some 'fudge factor' built into things. Depending on that 'fudge factor' isn't the smartest thing in the world to do. 'Over-volting' is not good practice as far as most things are concerned.
- 'Doc
(What was the purpose/reason for all that? I read the thread and got to thinking that the subject is another one of those 'dumb' things I've never thought about. Or put a little better, I've/you've caught me doing something else that's kind of dumb. Typical, but still dumb. (I do 'dumb' very well!))