I can't believe I never posted internal photos.
View attachment 937566
The side wall thickness is 0.1715"
Corner bosses are 0.654" radius from the exterior corner radii.
Hardware 4each 1/4"-28 x 3/4" overall countersink machine screws.
In order to use your CAD to make burnable string patterns for lost wax/investment cast aluminum housings (maybe you'll bid on an FBO.GOV contract to mfg them?) that internal core that forms the cavity has to have the same 5 degree taper as the outside so the wall thickness remains uniform and the 5 degree draft allows the core to be removed from the casting mold.
The core itself gets destroyed when you remove the casting from the green sand, not reusable.
Black rubber/neoprene gasket 0.046" thick.