this might be a moot point (many are), but the unit you're discussing
(the roland dm-800, no?) allows you to bounce tracks together as many
times as you'd like without any loss whatsoever (it's digital), so
having track space to work with is definitely not an issue.
the points about the conditions under which you'd be playing are good
ones, though, and that's probably something you should take into consider-
ation before taking the little beast on the road. but, i've seen it and
handled it; it's compact and sturdy, and i'm sure roland mounted the
drive(s) with care and consideration - you may want to actually call and
ask if you're that interested.
peace,
darshan