Exhaust question

My rv8 is suffering from belly skin cracks. Vans recommended exhaust turn downs from Vetterman, which are on order. In looking at my exhaust it already has extensions. Should I remove those first, or weld the turn downs onto them?

This may or may not help since my situation was a little different.

I didn't have any belly skin cracks but wanted to reduce the floor vibration. I already had the turndown exhaust, but they were short. So Clint at Vetterman's sent me two short, straight extensions. They are each attached by one bolt. Hint: Put the bolt in per the instructions so the bolt is pointed toward the center of the airplane and not visible to a bystander standing next to the airplane (not like I did).





And the instructions: