Flex tail fin question

I’ve been looking at every flex tail design I can find online. There aren’t too many results and now I’m more confused than ever. I don’t know if I should have a thin strip of foam remaining in the tail or if I should just go for straight glass layup. I’m planning on using a combination of carbon fiber and fiberglass so I’m not too concerned about strength. I’m more concerned about glassing in my fin. It’s a thruster setup with the 2 side fins set in foam. The third, trailing fin is the fin I have the question about. Any suggestions?

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