U- clamps should be tightened till they dent the pipe enough it seals when you block the tailpipe.
Properly installed, they will hold for months even if you remove the clamps.
If you use an impact wrench, it takes seconds.
Occasionally, uneven clamping will keep it from sealing, add another clamp at a different angle. Done.
Try not to point the threads down where thy can get hit.
I usually weld my own stuff, because I like doing it, but clamps ought to hold fine till the pipe rusts through.