I like it, 91 views and no comments. Considering there's nothing shown yet, that's not surprising.
Anyhow, I have the lengthwise frame cut out and took some shots to show the changes I've made. This first shot shows how much I removed from the sponson inside bottom. The straight line at the bottom of the picture is how the plan was drawn. Since this didn't match the full sized boat, I redrew it as can be seen below the cut out part. Something else that is very visible is the areas where I removed plywood from the middle of the part. This was done for two reasons. The first being to reduce the weight of the boat. With the sponson insides, much of the wood is inside the boat and not subject to being exposed to the water and, therefore, it's not really needed. The second reason is that if water does somehow get inside the boat, having sealed areas will trap water inside, making the boat heavier and eventually rotting the wood so this is a way to get water out.
The second picture shows how I notched the bottom of the sponson. This was done to align the bottom of the sponson to the bottom of the airtrap. The inner part of the sponson bottom is angled at 45 degrees, giving the 1/16th(1.5875mm) ply a thickness of 3/32" (2.38mm). How this all works will be shown later in the build


This shot shows the top of the engine bay wall. The cut away area is where the flash pan will be, something not shown anywhere except on the color sheet. For those not familiar with piston powered hydroplanes, it was not uncommon for an exhaust header to fail. When that happened, hot exhaust and still burning fuel would be sent at the deck of the boats and, since the boats were made out of wood, this would tend to set the boat on fire. Metal flash pans were used to prevent the exhaust from hitting the wooden structure.

This last shot shows the slot for the firewall and where the plan shows it to go. When Roger drew up the plan for the Cotts Beverage, the engine bay was covered. With the Pak, it normally ran without an engine cover so, to get the location of the firewall and the front of the cockpit correct, that frame had to be moved forward