Check with davea7 - several of the champ karters, including some in the jr. sportsman II class I crew chiefed in this season, run them at our home track. Bolt it to your seat, pad it in your favorite style (most use foam pipe insulation, a couple have done a nice job with closed cell foam blocks, one has a really neat combination of the two approaches) and you're good to go. Definitely a quality product which we'll be adding to our driver's seat for next season. http://karting.4cycle.com/showthread.php?839-Champ-Kart-Seat-Halos
We use a Randy LaJoie halo setup on our Jr Sportsman, as many do around our area. Jeff at Rage has some coming in soon, you can contact him. Check out his site ragekarts.com Just add to existing fiberglass seat and go. I have not yet seen a full aluminum race seat mounted in a small cage kart yet. If anyone has pic's I would be interested in seeing them.
We have one that runs in Jr Sportsman II Champ at our local track; I don't think I have a picture of it, but if I find one I'll contact you. That having been said, the father/crewchief is a talented fabricator, and he did very artfully cut down the seat to perfectly fit the relatively small stature of his driver and the smaller dimensions of the Jr Sportsman Champ.
if your running a regular champ class i wouldnt use a full containment seat,your kart needs to flex and for vcg you need to be lower,you may of seen them in high hp or the qrc or bolt on cage classes...
qrc seat is just a kirkey car seat . You may want to check the rules if you plan to run down there with the guys running turf tires and that in champs you are required to have an aluminum seat. if you don't plan to run there in this area there really isn't any place that runs champs that I know of besides Delaware and sw wisconsin and if that's where you plan to run get a champ seat with the halo like the guys above suggested.