A thought hit me as to how and why I am going to limit ship size in MTU, other than via GM fiat.  In MgT, Capital ships are required to be in section.  The largest one that can be done in 2 sections is 7,500 dTons, which, as it happens, is the largest amount of volume that an anti-gravity field can support.  Jump drives require A/G fields to make jump bubbles, so that also limits how big a jump capable ship can be.  A/G fields effecting a volume, not a mass also explains why space ships are sized in dTons and the actual mass of the ship doesn't matter or affect how many G's acceleration it can pull.   Due to the rather massive drop in both size and cost of spinal mounts,  even meson guns up to Type C (the largest being  D) could be mounted in a TL 15 craft. 

Need to add a 7.5k dTon "Dreadnought" to my things to design.