gary, I had a problem with my first used kart years ago (top kart) 30mm mains, 32mm crossrails as I had the floor tray tabs breaking often. I also had a small crack on the outer rail near the motor area. I had the crack fixed as I first drilled 2 very small holes on each end of the crack, then prepped the crack by slightly beveling along the crack ,then welded the area ground it smooth and then made a small gusset 1″ -1.5″ long x 3/4″wide and contoured it to the frame and welded it to the tube overlapping the crack and I never had any issues with it again.
my 2006 “krt” chassis I bought new and have countless laps on it and it has never broken anywhere and is still fast.
check out the new display chassis featured in the business/ retail section from ok1 and praga .