This happened in Panama.
Let me explain a bit about the "traditionality" of for example this boat.
While it is a dugout, it is a recent one. After dealing with the whole paper work for using the tree and that, the boat that get dug is about 2 - 2.5 inches thick all around and while it is a perfectly usable traditional boat for the natives, it then get sent to the racing cayuco gods who start grinding and shaping it until the final boat meets racing specs .no fiberglass is allowed for the original boat, and post production, just 1sq meter is allowed for repairs.
As for adding wood, when facing damage like this, as long as you can keep atleast a 20 feet long x 2 feet wide, you can do as you please, but documeting everything for race records.
While no glass is allowed, repairs are donde with 1inch square strips, then grinded to shape and the end result is pretty stiff and strong, bever had one brake (without counting mine :( )
Race shaping, note the pattern on the wood all the same log no strips