Seacast if fine if you have a fiberglass layer on each side.(recomended by seacast after I did mine)
As you can see, I raised my transom 5". The seacast by itself isn't strong enough, I had to plate mine with aluminum after it cracked. Other than that, it's great stuff. I used a chainsaw, verrrry carefully, ;D to remove the wet/rotten transom wood. Make sure the glass is 100% dry before using the seacast. Also, make sure that there is no holes in the glass shell, the seacast will run out. Sea-r-cy ;)