While you're in dimension mode... can you answer this question?
When the TSC in a 1015 style box is mounted at the right height, what clearance is available from axle to bottom of coupler box? Figure a 33" FVM wheelset.
And, since it looks like your boxes are shorter in height, now how much did you gain in this measurement?
I have one MTL car that I mounted the normal box and coupler to that matches my gauge. Measuring off of that here's about what I get in comparison.
My coupler box on the left is .095" tall while the MTL box is .125".
Thin Black line - top of BLMA .050" axle on 33" wheel.
Thick black line - coupler center - .216"
Red box - difference in bottom of coupler box - .003"
Blue box - difference in floor height - .027"
So to try and answer, I get .0369" of clearance for the MTL box to the axle while mine is negligibly more at .0399".
Someone can let me know if I messed up anything.
Jason