As Shaw pointed out, the bridge alcove diagram is of an earlier version of the ship. Do not place too much stock in it. As for why there are no horizontal turbo paths evident on the cross section in TMOST? The answer is simple: none of them fall along the centerline of the ship. The bridge turbo tube, as is evident from the outside of the model, IS
on the center line.
Datin confirmed to me that both the small model and the eleven footer were constructed from the same plan. He told me the earlier version was what he quoted from, but it wasn't used during construction. I do not know why the contours came out so different between the models.
I also asked whether the blueprint had a flat underside around the bottom edge of the saucer, or whether it was a continuous curve, like the 11 footer. I never got a clear answer to that one.