H77,
Thanks for your message.

The deck plate (or inspection ports) were purchased from "West Marine", (www.westmarine.com). The instructions called for a 6-1/2" rough opening; so I routed my old openings to the appropriate fit. These plate do not have a flange surface which is designed for a curved hull mount so I used marine grade white silicon to form, seal, and fill the gap. Hobie hulls have an inner and outer surface of fiberglass with foam in between. I applied the silicon then fitted the port. I used a wetted finger to form the fillet between the flange and the hull; this turned-out OK as you can see in the picture. After the silicon had dried I used the correct drill size to open bolt holes through the sealant. I was careful not to disturb the silicon's integrity. The through-hull mounting bolts will not provide much of a structural benefit as they would just crush the foam as the nut/bolt is tightened. I used SS parts with a 5/8" plate washer and a nut with a nylon thread lock. I tightened them just enough to start compression on the hull. After installation was complete, I greased the o-ring and the port-cover threads with petroleum jelly per the instructions. The whole assembly feels solid and should provide many seasons of service. I plan to add port bags (also available from West Marine), in the future. I hope this was helpful.

Cheers,

Eric