Yet another reason I won't let my dealer touch my trailer

There are a lot of situations where you can't through-bolt.
In my case the bolt ends up in the webbing of the C channel that makes up my toungue. For most, using the self tapping screws would work fine as long as they're checked once in a while.
I ended up tapping the C channel and using grade 5 bolts - the frame is at least as thick as a bolt, more so at the webbing. Then I painted everything black and used some red touch up paint to make a mark so I can readily see if the bolt has moved.