It would get broken or damaged unless you had someway to fold it, or really tall goofy looking landing gear. Take a look at the predator UAV (with the inverted v-tail), When they switched to the B model, they put the tail on top of the fuselage to reduce the possibility of tail strikes, among other improvements. As far as a model, you could always hand launch it, maybe recover via parachute? I'm not sure that it really matters which side the tail is on(top or bottom), except for the effect of the fuselage blanketing the tail area during nose high manuevers and high-alpha(like climbing out from takeoff), which MAY have an affect on the elevator and rudder and result in less control.(Think J-3 Cub) Most planes don't point downwards too much, unless you're talking about aerobatics stuff.

Actually many planes have small fins on the underside to help maintain roll stability, and possibly(?) increase fuel economy. Take a look at most military fighters(F-16, F-15, F-14, F-18, etc all have 'em) in addition to many of the small buisness jets(gulfstream, etc) have them too. Heck, even my PT-40 had "fins" for a while.

Just my guess - tail on top cause it's easier.