Our trailer is a 2014. Sometime in the first 4 or 5 months of ownership, we lost a dump handle and part of the rod assembly. I couldn't find any replacement rods in the correct length, so I went to ACE Hardware and bought a 36" piece of threaded rod and a couple of lock nuts and just cut it to the correct length with a hack saw and thought it would be a temporary fix until I could find the correct rod.
Well, it's still on the trailer, still working and somewhere in the passthrough, there's a length of rod that I finally found at a campground store somewhere out west.
Point is, it's not a difficult fix and there's not a need to cut the COROPLAST belly. Just find a sheet of cardboard to lay on, crawl under the trailer with your parts and plan to spend some "frustrating minutes or more" trying to hold your tongue just right so the end of the rod "finds the right place in the dark"....
Easy to do, but it takes time and patience....