The jack is useless if you're trying to use the frame. I guess you could fully extend the jack and then look at your flat tire for a bit before lowering the jack with the flat tire still on the truck.
Every truck I've ever owned shows the jack being placed on the axel directly beneath the spring. Why wouldn't you do that? The axel is strong enough to support the entire truck and is specifically designed to do so right where the springs attach. Plus doing so eliminates the need to overcome suspension travel.
Up front can be a little harder, but a lot of trucks have jack mounts formed into the lower control arm for the same reason: the frame sits too high up for the jack to be of any use there.