Asjimmy said, when he's only got one bass drum onstage, he's more than likely using a "double beater" which is two pedals on one bass drum, so you can do the double bass licks on one drum, but why he'd go to one kick, if he has two, is kinda weird.. maybe different tours and he liked one or two kicks.. Most of the time drummers will find a way to get both bass drums onstage, regardless of the stage size, but it COULD be a factor..
Friendship is like peeing your pants.. Everybody can see it, but only you can feel the warmth..