if anyone's interested,
i can see the resistors on the schematic that are responsible for the
pan settings of each of the sounds:

bd - r202, r203
sd - r205, 206

etc., it should be obvious what the other ones are from the schematic
i'm thinking you just remove the resistors, connect the middle lug of
a pot to the output jack's normally closed connection, and the two
outside lugs to the paths the resistors used to connect to.

let me stress, i have NOT performed this mod, i am only mentioning
the info in case anyone is interested in testing it out before i have
a chance. i would suggest trying 50k or 100k pots. when i eventually
do it i want to try to get pots and knobs that are micro enough to
fit under the volume sliders. if no one wants to test it out i'll get
to it at some point.

i don't know if anyone else uses the main outs, but pan pots would be
extremely cool for me; my live setup folds out of a small suitcase so
my mixer is too small to plug every sound into a different channel.
greg