A junk fin and tape holds the box true. It's really just that simple. This is how windsurf boxes are set, not surfboards. This box installation is much stronger than a surfboard installation. For one, it's a windsurf box, not a surfboard box. Windsurf boxes by Chinook use fiberglass filled Dupont Zytel. It's so dam tough, it's near impossible to sand flush after setting. A surfboard box is cheap plastic, usually a 2 piece box and doesn't have the high glass fill.
Autry, no flat water race boards are in the cards. Why build a board for use on 4 days a year. The 4 Coastal Urge races. I'd never paddle flat water, if it wasn't for those 4 races.
This board is built for one thing, planing, and planing only happens with wind or waves at your back in the ocean. Super fun.