Space constraints and COG are certainly a good arguements as to putting it there or even it hitting something would make a good arguement for not putting it there.
I'm not sure that getting stuck is any real arguement, but I think the real issue would be whether or not it will able to be removed out from under the truck if you need it and whether or not the tire would be too close to the ground for it to come out and be used. If it can't be removed from under the truck because it's too close to the ground then maybe moving the truck is an option so the tire can be pulled out. But what if the truck can't be moved for some reason? Then what?
Besides, if you didn't have the room for your spare in the truck then you still have to put the flat tire somewhere, don't you? I sure wouldn't want to put it back underneath the truck if it was hard to get out in the first place. But I suppose there's a solution to just about every problem. Like maybe using someone else spare till you get away from a bad situation (if that's the case) and then swapping your spare in place of it.
Just another
