Well I paid for the anchor roller yesterday and it came today

The seller on ebay is DEFINATELY getting a very good feedback from me!
In the meantime I posted over on boated.com and they said to call FW to speak to the engineer and ask him.. so I did. The engineer I talked to at Four Winns said he did a lot of work on the era Vista 258 I have and that there really isnt much I can add in the terms of backing plate because its up in anchor locker. He advised me to use stainless hardware (duh) and countersink the holes in the fiberglass so it doesnt crack. Other than that, he said 3M 4200 quick set will be a fine sealing material.