ORIGINAL: Michaelj2k
I'll agree with Nic on the first picture, TB may have been looking at hinging and moments of inertia on the ailerons. I believe the second and third sketches may be for calculating bulkhead area, ((a ''section cut'') at a particular fuselage station. As far as the large circle, Tom may have just grabbed a reasonably clear sheet of paper and started sketching for some other idea.
You are correct that one caption DID call it the "Lateral Area Special". No other model I can think of at that time had that kind of lateral area....in the fin or anywhere else.
Now that I look at it, the large circle drawing may go with the drawing above, and MAY have something to do with the fuel tank, but who knows, (actually the tank is smaller than that though). The drawing has been preserved with everything else, and it's interesting to look at and speculate about.
The next drawing to discuss is my favorite...stay tuned.
Duane