This is something I have been looking into for my 715 as well. I drive like a dang fool, so a seatbelt is a good idea for me. I'm sort of partial to my face, ribs and other breakables above the waist so I'm thinking of a 3 point belt. Since most factory 3 point belts mount to a pilliar above and behind the driver, some mods are in order since most of us don't really want a rollcage in the cab just to mount belts to. The shoulder belt can be mounted behind the driver at a lower level, but you have to be careful how you do it. It can be mounted level with your shoulder or a little below but you can't go past a 10 degree slope. Any more than that and you can hurt your back and break your collar bone in an accident. Side to side mounting is up to the individual, but you don't want it cutting into your neck, and you don't want it falling off your shoulder either. The lap belts should be mounted a little behind your waist and the angle is important there also. I got all of this from Simpson Race Products. It's for their racing harnesses, but should work for a 3 point belt as well. In any case, a little back trouble or collar bone is well worth it if you don't go sailing through the windshield. I'll post the pic from Simpson's website in case my description has you all confuzuled.
This illustration should work pretty well for our purposes. I came up with this after looking at the 715 and trying to find a safer way to put in a factory style 3 point belt. The soft top bows are not strong enough, and rather than risk fabricating something that would be ugly as well as unsafe, I determined that the 715 cab was plenty strong enough to anchor a shoulder belt to if it was done properly. My plan is to mount a plate in the corner of the cab, welded to both the side and back wall of the cab and angled so it doesn't bind the beltup when it is attached. Sort of like this is you can follow my crappy diagram:
Simple, yet effective, or at least that's the idea...
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