@Freddie, Cannon ports were on my agenda yesterday. I spent several hours working on the Main deck ports.
After watching the latest video (#49), I build out the ports the same way.
First adding the backing
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Then sanding and dry fitting each Port to it’s proper location. I would suggest you number the ports because each one will fit differently.
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The test fit.
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The ports sit even with the Wale, but without adjusting the rear of the port it might not fit all thevway through the hull.
The video explains it much better than I can
Gunport Video
Jan