The edges are where the floor generally rots so I treated the the edges with a barrier coat of West Epoxy (2 coats). I extended it in about 10 inches top and bottom. Hopefully with all the leaks fixed it won't be tested, but time takes it's toll and if there are leaks in the future, the underlying wood will be somewhat protected.
If you run a round over router on the edges of the new floor it will slide into the c-channel much more easily.
Bruce & Rachel
68 Trade Wind
2001 Toyota Tundra