Dom, I re-did my 1978 Trillium
4500 last year. You can read about it and see my photos of the bellyband repair in the link at the bottom of this post.
On my 1978 Trillium 4500, fiberglass tape seam tape and square metal plates were applied along the belly seam everywhere except directly below the rear window.
If you read my thread in the link at the bottom of this post, you will note that I did the following:
- removed the rear window
- cleaned out the rotten plywood strip and old glue that held it along the seam below the rear window
- used construction adhesive to glue the seam back together after inserting a new strip of wood wedged between 2 pieces of aluminum c-channel
- re-sealed/re-installed the window
Then for the rest of the belly seam on the trailer, I cut out all of the square metal plates (40 or 50 of them) using a dremel with a cutting disc, then fiberglassed the seam together all the way around.