You don't need to mount the stabilizers right at the corners. Just put them where they won't interfere with the tank and the dump valves. As for attaching them, I would not weld them. Makes it too hard to remove/replace a bent one. Most that I've seen are mounted with big self tapping screws.
2006 Silverado 1500HD Crew Cab 2WD 6.0L 3.73 8600 GVWR
2018 Coachmen Catalina Legacy Edition 223RBS
1991 Palomino Filly PUP