Colvert and T-Cut, nagging doubt would not leave me alone.
I have just used a mirror to look at the top of the triangle where exhaust pipe and item 1 meet. see
https://rimmerbros.com/Item--i-GRID001957 items 1 and 2
There is no way they are coming out downwards. There is a flange on these bolts that is larger then the hole the have to come out of. If anything the bolt/stud needs to go upwards.
Are you thinking of the studs at the other end of the unit?
T-cut going back to your post 4, perhaps I should use the bottom nut, the outer one and tighten it. If threaded, tightening the nut will undo the thread in the triangle if there is one.
Can you advise?
macafee2