Under my rear seat and well tied down so it will not move! I have been trying to find a good place to mount one since I put the FWC on-just no real good place to do it without tearing up things, but here are some thoughts and ideas I've tried or seen or heard about! They have all sorts of mounting brackets you can use to attach it to the side of the truck, but no mater how well you tie them down they shack and rattle. Seems to me there was a thread about this a while back; one of the main problems with Hi-lift jack attachment is that it is usually mounted upright/laying down in the back bed of the truck (like in my old govt rig or my truck before i got my FWC) and the FWC now takes up most of that space.
If you want to do some neat modification adapt your front bumper to carry it and a shovel/pick/palaske/tow rope and just about thing else (they make bumper kits that help you to adapt the bumper). Another place is on the side panel of the truck-again once you start messing with your truck-there goes the resale value. Again, almost any place that you can fit one, you can try to mount it, just remember trying to get at it when you need it. I've seen some mounted on the rear bumper of the truck-but again, I don't think the the FWC camper shell is strong enough to hold up the jack unless u use one of the FWC internal supports or beef it up some way. There was a thread awhile back talking about mounting a gas can-same problems!
Don't try to mount it on the fwc roof-it may look neat and the roof may support it, but try and get it down when you are hot, dirty and pissed off-they do weigh more than you think, and they are awkward. By the way, you need to get some adapters to make the thing work on some of the newer rigs, seems like it will not fit under the front bumper because you need a straight angle to use one, but they are cheap and well worth the cost! Hope this helps and good luck!
Smoke