Looking at pics of the P4 with the roof on couldn't a person make a mount on the roof just behind the front roll bar were it drops down and meets the rear roll bar. I know height is a concern but using a skinny tire would work. The spare would basicially be like that of a car [donut spare tire] Really all you need a spare for is to beable to carry the machine back to were you started. Having it on the roof would keep from taking up any bed space etc:. I think if I had bought a P4 and wanted to carry a spare I'd do some thing like that.Another thing to consider would there be enough room to say mount the spare on the underside of the roof right near the front. I don't have a P4 to see if that would work. Not sure how much that would impede the head clearance for anyone riding in the back. Just some idea's I'am throwing out there.