I used 5200 to seal the holes. They are Atwood 30 degree holders. I went with 30s for trolling. They held up well over the weekend. Caught 3 nice dolphin out of Cape Canaveral this weekend. The transom area that I cut into was about an inch or so thick. I used a hole saw to dill it out. You have to use a corded drill. it's like drilling through concrete and gets very hot. I bought a 36" strip of aluminum from HD and cut them down for the backing plates. I discovered after that Robalo uses Gemlux (not sure of the spelling) rodholders stock. I found them online after I put these on. They are a bit lower in price. They also make their own backing plates to match the holders which is nice.