I'm about to take an 800-900 mile trip and have to put my 31" spare on the roof. Is the roof strong enough to hold it between the cross bars or should I mount it on top of the cross bars? I'd prefer it lower and more secure on the roof, but if the roof can't hold the weight, I'll mount it on top of the bars. It is a stock roof rack.

99 Sportage 2Dr, 1.5" body lift, 30x9.50 Cooper M/T's, high lift, CB, custom bumpers, Warn manual hubs, Tom Tom GPS, snorkel.
99 Jeep Cherokee 3" lift, 31" mud terrains