I think they can certainly run parallel, though I do question the disparity in size between ACS and BCS. Currently I'm experimenting with the idea of mixing the extrapolated CT charts (brings the max ship to 10K dtons) with ganging engines together and the MgT partitioning rules for oversize ships - which gives me a 60K dton maximum size ship.
This actually works well in my brain - still very large compared to ACS ships (so much better at cargo transport and weapon mounting), but far less than the 500k dton battleships of HG and the like.
D.
It is all about load factor. Look at the4 Worlds are within J2 of Heguz (Spin 2706,E66A224-9):
Pavanne (Spin 2905, E310000-0)
Carsten (Spin 2906, C427402)
Focaline (Spin2607, EA88544-7)
Violante (Spin 2708,C669452-A)
If you try to build routes between those world and Heguz, you will not justify any large freighter. Few hundreds on Heguz live about the E starport, used as refuelling point since it is a waterworld without gas giant. It is a pit stop on the J-4 route between the Paya Naval base and Nazemine Scout base. Those Imperial ship do not carry civilian cargo to Heguz. The J2 route between Inthe and Nazemind Scout bases (5 jumps for S courrier rather than 10 via X-boat)also stop at Heguz
To supply Heguz and keep the subsector capital in the loop you most likely have a monthly subsidized M class J-3 trader that jump to Zila then to the subsector capital Aramis. A runing mate is departing Aramis at the same time. Because Moughas (Spin 2406) is another waterworld, some problem specific high TL gear may be acquired there by a clever Far Trader that knows the problems of Heguz. He will J-2 to Focaline and pick if possible some vegies before J-2 to Heguz. Since 60 dt of canned food would represent 30,000cubic feet, that is 500 deadweight tons for 500 inhabitants, each will have 1000 kilo at 5 kilo a day, that is more than 6 month of foods. The far trader might actually be very hapy with a 1 dT of popcorn and 100 old movies CD.
This mean that there must be small scale trade,
At the same time, Focaline would be able to sell at least 200,000 dtons of food a month to Rethe if its 700,000 inhabitants were able and willing to. Even if Z type engine were the final frontier of Jump drive, you would use 150 x 2,400ships (1,400 dt cargo each) rather than 3,000 Far trader.
Have fun
Selandia