Hi There,
A little Trick that i picked up along my travels so far is that If you get the drummer to walk around the room with the floor tom (whilst you stand a few metres away from it listening) get him to give it a few clean hits while standing in a specific place, then move around a bit and repeat the process. what you're listening for is where the tom sounds the phattest, (which in turn means that it is in a part of the room where the bottem end is the most in phase). when you find a good spot for the floor tom get the drummer to set his kit up around the floor tom and 9 out of ten times this ends up being the best place to set the kit up in the room, well it's worked for myself (and the engineer that i learned it off as well of course) give it a shot and see if it works for you as well as it has for me.
,
regards
Axle