Unused finboxes vs performance

I’ve often wondered the same. Not so much the empty FCS2 v. Empty futures on five fin setups when going thruster instead of quad or missing side bites on a 2 +1.

I’m curious about the drag or influence on a high volume egg style all rounder with a central fin box and the additional plugs so it can be quad, tri, 2 + 1, or single fin. I imagine that if it’s ridden as a quad without anything in the longer central fin box it would have some drag or effect on the surfboard. I’ve always assumed that there must be some compromises in design or optimal fin placements on these types of boards.

My shaper suggested unused fin boxes can affect the flex pattern in the tail.

I would suggest fins cause way more drag than unused boxes.

You can get infilled things, but in reality if there is any drag factor it's extremely minimal if it was a factor pro surfers would have infills same goes with flex pattern etc

Even Kelly rides quads with no infills for us everyday average surfers it's sure not going to something we could ever notice.

I think they fill with water and don’t interact all that much as the water rushes past, however I have a friend who fills them in with silastic and another who puts duct tape over the top?