Great outcome for your massive project. Noticed the use of calipers (self-made, good job) and remembered about dugout canoe builders of the USA Northwest using the process of completing the exterior of the hull first.

Then drilling holes from the exterior inward and driving wooden rods with painted tips into the holes to the intended hull thickness. These painted tips would be exposed when the proper thickness was excavated from the interior.

The hull would then be expanded by filling it with water, which was brought to a sustained boil with hot rocks so the wood became flexible enough to expand using wedges.