Hey Bearcave........

You do need the 'platform' of the Bi-Fin to be a few mm's clear from the boards hull surface to prevent any surface contact that could result in a jam, especially with the possibility of getting weed or debris stuck in between. I dont think the nuts create any drag issue in reality.......although in theory as you say. it would spell 'obstacle'

If I was going to weld any material to go with a flush/streamlined design - 'Stainless Steel' would be the better option as by thickness it will provide a stronger unit all in all - especially for the required strength of the pivot pin needs.

Bro ********. ...
Share the STOKE !

Have a great weekend all.....I'm hoping for some good surf this evening.......hope you all catch great waves !