awhile back i ordered a couple of these as a possible solution to using scooter throttles with an ESC but havent had a chance to test it:
http://alienpowersystem.com/shop/electr ... face-1-4v/
hot off the charger, a 1s lipo would be at 4.20v, so 12s at 50.2v would be hitting the max rating for the vesc. for peace of mind and long life for the controller i'd want the answers to come from the mfr, have them confirm if 50v is a hard limit and whether exceeding that would damage the components or is the focbox overbuilt to handle more.
re: performance, adding another 4v offers a modest increase in RPM which is reason enough for me to use it. another reason i use 13s is to increase the gap between max voltage and LVC.
when i run lipos i always use buzzers with the alarms set to trigger at 3.6v/cell. this is a higher LVC than the brushed controllers i'm using with these lipos, because i dont trust the accuracy of these cheap controllers to be the only thing keeping me from overdischarging and damaging my batt pack.
i believe the general recommendation is anywhere from 3.0 - 3.6v as the alarm cutoff for lipos but it tends to be a personal preference - do you want to err on the side of caution or try to squeeze out the most runtime from your lipos. with kids around i play it safe...