Do not weld to the frame! ever. Your sliders need to be bolted. You can crawl under mine in Moab if you want but if you weld to the frame it will crack at some point. Frames are made to flex and are heat treated. Once you disturb this heat treatment and flex the frame it will start to develop cracks near the weld. Now on the other hand if you look at our jeep where the cage is welded to the frame the entire structure is now rigid so there is no flexing.
Todd