I installed these Port lights in a 21 foot Pacific Dory. Installation was straight forward, but did require a lot of sealant to guarantee the clamp fit. Templates are good and adequate. I'm not sure of parts availability. I installed these port lights this summer and it rains here in the Pacific Northwest, I am currently noting some leakage coming from the bottom of the seal edge. The gaskets were tight to the glass when installed, after a few trips out in 4-5 footers, there is some misalignment and I don't think it can be adjusted.
Stefan the Boat builder