Drive-J huh?
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That makes the design TL=11.
6x Gunners in single occupancy staterooms (24 tons) plus 6 turrets (6 tons).
That means you're spending 30 tons on defense ... centered upon the ship itself, which is equipped with a 1G maneuver drive and a model/3 computer.
As an alternative, that would remain purely within the boundaries of LBB2 ...
You could spend those 30 tons on a LBB2 Ship's Boat instead.
The 13.7 tons of "excess space" available for fittings could include 2 starship staterooms (8 tons, 1 pilot, 1 gunner), leaving 5.7 tons remaining for a model/4 computer and 1 ton of fire control for a turret. Increase the fuel tankage from 1.8 tons to 2.5 tons ... and now you've got a (combat relevant) 6G fighter escort that can engage hostiles
away from and screen the parent (1G) craft, enabling Block & Tackle maneuvering.
What is the purpose of the Slow Boat?
You don't have 2 pilots on payroll, so who pilots the Slow Boat independently of the parent starship?
Is the Slow Boat just there for interface/runabout work?
To be honest, I would probably ditch the Slow Boat and do a combination of expansion of the cargo hold and the installation of a fuel purification plant (TL=11). The ship is already streamlined, so might as well make wilderness refueling an option to bring down operating costs pretty substantially.
Alternatively, you could reallocate the 30 tons of the Slow Boat towards a Maneuver-J drive and get 3G out of the starship ... which ought to reduce the risk of "unwanted intercepts" while maneuvering in normal space.
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Use whatever "leftover" tonnage you have on additional cargo, +1 high passenger stateroom, full time steward stateroom and fuel purification plant to round out the design. Maybe add a vehicle or two (Speeder + Air/Raft? Speeder + GCarrier for passenger transport in comfort?).