From the TNG Tech Manual, pages 22 and 23, I'm pulling these relevant numbers (I'm not going to reproduce the whole section of text, as most of it is nonsense... (though, I admit, triumphantly clever and well thought out nonsense--thank you Rick Sternbach and Mike Okuda!) but there's only so much phase-transition-bonding I can type through in one sitting...
Going from inside the hull to outside the hull, the numbers I see are...
4.7 cm exterior shell substrate
1.2 cm (x3) biaxially stressed tritanium fabric (for additional torsion strength... duh)
2.3 cm (x4) Substrate fabric layers (only around major structural elements)
3.76 cm (x2) thermal insulation and SIF conductivity layers
8.7 cm tritanium truss framework
4.2 cm radiation attenuation layering and more SIF waveguides.
1.6 cm ablative ceramic fabric fused to a
0.15 cm tritanium foil substrate.
Add them up...
or 15.6 inches around major structural elements
or 11.99 inches at most of the hull.
Since the edge of the windows on the sets seems to my eye to be about a foot or so thick, I think 11.99 inches is reasonable. It's safe to say that an 11 or 12 inch thick hull at the set's windows would be quite allowable using this data. I have no idea how you guys got to 3 or 4 feet.