I work with batteries and chargers quite a bit at my job so here are my 2cents
Remember that lipos are very very susceptible to damage. If you're putting them in your hopper, hardcase lipos may be the safer option since theyre protected. the one posted by OP is not hard case, and lipo fires
are no joke. you wouldn't want to be sliding around on the field only to see that you're shooting fireballs. well, actually...
As several of you guys have said, 11.1V is quite high. Actually, a 3s lipo charges to 12.6V when full (4.2 per cell). If you're really interested in seeing if your board can handle the voltage, you're going to have to open it up and look at the individual components. you'll have to look on the web for spec sheets for their voltage ratings. things that probably experience the full battery voltage are: the regulator, the caps, the motor driver. probably some other stuff too, i dont remember what else is on the board.
Also, 3s batteries have a minimum voltage of 9V (3V per cell). any lower and you risk permanently discharging your battery. Since the hopper is made to work with 6AA batteries, it's low voltage cutoff is probably well below 9V and this means that your hopper will probably brick your pack unless you're super careful or use a BMS like the one smartpartsuser mentioned.
It would probably be safer, as someone else has already pointed out, to use a 2s lipo, which charges up to 8.4V. 2 reasons: 1) safer for your components since it's definitely within components ratings, 2) the low-voltage protection will probably
work since the 2s can safely go down to 6V. If anyone is interested in knowing exactly what voltage it is, I could probably open up my old halo to see.
hobby king is great if you can find the battery you want in the US warehouse. shipping from china usually takes 2-4 weeks. hobbypartz is another place i order my stuff from, they're located in socal and have similar prices to hobbyking.
also, afaik, lipos do not explode when discharged too low, they just brick and never come back. I've discharged many lipos below the minimum. they explode when charged too high or when punctured/damaged. someone correct me if i'm wrong.
that's it for now.