For a speculative trade group I offer a 100 ton TL 15 design based at Glissten
The ship is J6-1G and a paltry few Dt of cargo space, it uses HepLar for the maneuver drive and has a series of grapples mounted on it's unstreamlined hull.
Designed with T4 Fire Fusion and Steel rules.
First set of grapples are for drop tanks, additional grapples are mounted for cargo modules. Up to 250 Dt of cargo modules may be carried, and drop tanks can hold up 60 Dt of fuel. 10 Dt of jump fuel is carried internally for use as maneuver fuel or jump 1 escape.
The ship is unarmed and unarmoured and relies on high port facilities to swap out cargo modules and attach a fresh set of drop tanks. Lacking sufficient internal fuel tankage for maximum jump this ship is limited to a single J-1 @ 100 ton displacement on internal tankage.
In play the party hires factors at each world on their itenary, establishing a set schedule of service, the factor is responsible to have provided for the loaded cargo modules and fuel tanks to be waiting for their ship.
Distance J6, 60 tons fuel, incidental level of cargo, no external retained tanks or modules. Good to return to the start of a loop that is profitable only in 1 direction.
distance J5 58 tons fuel minor cargo level, 16 2/3 tons of external modules could be retained. Not a very usefull configuration, you may as well dead head back all the way J-6 configuration but use J5 fuel.
Distance J4 56 tons fuel, minor cargo level, 40 Dt of retained cargo module.
At 44 Dt of cargo starting to make a bit of scratch.
Distance J3 52.5 tons fuel, major cargo level, 75 Dt of retained tanks or cargo modules. Costs going down income up, what's not to like.
Distance J2 46 1/3 tons fuel, Major cargo level, 133 1/3 tons of retained tanks or cargo modules. More cargo than ship hull, and at J2.
Distance J1 35 tons fuel, Major Cargo level +Minor cargoes + trade and spec cargoes. 250 Dt of retined tanks or modules. OMG 1/4 mil in just cargo fees!
Use the J1 configuration running trade and spec cargoes between Glisten and it's Hi pop world next door, then follow the main into district 268, sell your cargo modules to help build up the local high port and J6 back to Glisten, pick up new cargo modules when you do your annual maint at Glisten.
Pirates? detach the modules and J1 out, with the modules still within range of the jump drive, the pirates (or customs patrol) will not get much loot/evidence.