The earliest drawings of PocketShip indicated a steel centerboard. The challenge of having to torch a plate of steel to shape and get any sort of shape on the leading and trailing edges was a major drawback. But the biggest issue would be the weight of the steel board---I think it was about a hundred pounds. This required a tackle arrangement for hoisting, and Murphy's Law demands that the tackle would get tangled or fail somehow right when you need it. In college I worked as a rigger and and did penance in the bilges of big cruising yachts with terminally jammed centerboard hoisting apparatuses. NO FUN.
A lighter aluminum board would be nice. You can work aluminum with woodworking tools. You'd have to mind corrosion---etching and coating would be required. But that would be even more true for a steel centerboard!
What usually jams centerboards is beach sand, gravel, or mud. I wonder if a looser-fitting board is actually MORE subject to jamming, as more sand and gravel can get into the slot.
Ultimately, a centerboard is a moving part that lives underwater. Sometimes they jam. <Shrugs> My insistence on inspection ports in the CB trunk is to allow you to unjam the board if needed. In two hundred launches of PocketShip #1, the board has hung up a couple of times, and was easy to dislodge through the inspection ports.
What might be the BEST solution would be a neat 3/8" hole with a grommet in the bridge deck. You can insert a metal push-rod in the hole and push the board down if it ever gets jammed. I know of centerboard boats that have the push-rod in a neat mount on the centerboard trunk.
Once in awhile I daydream about a fixed-keel PocketShip. That could be very cool, and still trailerable.