J3 freighters just don't have the income potential... J2 is just above breakeven - at least under CT, T20, and MGT1. In order to make J3 work under CT and T20, one has to follow the goods and tramp. Routed freighters are a losing proposition.
This has been my experience with the phenomenon as well.
If you're going all internal (no external) cargo capacity, a 400 ton starship with standard drives can
just barely break even shipping 3rd party cargoes while under subsidy. My
Five Sisters Clipper can just manage it with barely any profit margin to spare under subsidy at J4. If you allow external cargo loading (which the design is explicitly meant to do) then a paid off ship can easily make a profit shipping 3rd party cargoes at J2 ... and under bank financing (which is a LOT more expensive) can make a profit shipping 3rd party cargoes at J1 (more powerful drives than the code: 1 minimum used by Free Traders get EXPENSIVE in a hurry!
).
However, if you're in the tramp speculator market that whole 3rd party cargo shipping @ Cr1000 per ton quickly goes out the window as your main revenue source, turning it into "filler" when your hold doesn't otherwise fill up all the way. When you're wheeling and dealing in speculative cargoes, having a "just enough" cargo capacity and a high jump number makes a lot more economic sense, because all you need to do is buy low (duh) on speculative cargoes and then look around for what would be a presumably high demand market for that specific cargo so as to sell high (duh) and make a profit on the arbitrage. Being able to jump 3-4 parsecs in a week (or even 6-8 parsecs in 2 weeks) dramatically increases your options in determining where to go with your speculative cargo in order to command higher prices for it (on average) than what you bought it for at a higher rate of turnover (-DMs to buy, +DMs to sell, rapid transport).
The result from that design experiment in external load capacity was that you wound up with a starship that could "flex" between roles as a high jump/low capacity tramp speculator and being a low jump/high capacity bulk container transport depending on which way the tramp trade winds were blowing. The only real difference was the amount of external load to be transported. Speculators would want to have as wide a variety of trade code destinations "within range" (and higher jump numbers increases that range) so as to be able to wheel and deal profitably in a kind of "stacked deck" arrangement due to the high drive performance their starship is capable of ... without exceeding the regional tech level support available to them (so you don't have to "go far" for maintenance and repairs).
I'm currently finalizing additional research into this realm of "small ship, lots of external container capacity" by bumping the hull size up from 400 tons into the 500-600 range (functionally 401-600 equals 600 tons under LBB2.81 for standard drives) to see if the proof of concept executed in my
Five Sisters Clipper scales up advantageously from 400 to 600(-ish) tons for the starship. Thus far, all signs point to the answer being
YES owing to the fact that a +40% increase in hull size (and cost) is yielding a +100% increase in internal cargo capacity and a +140% increase in external cargo capacity at the expense of needing to advance from TL=10 to TL=12 (a relatively modest increase). The downside to the scaled up design is that in order to be profitable shipping 3rd party cargoes, there needs to be A LOT of cargo to move in order to break even. However an upside is that by doubling the internal cargo capacity (and enabling even limited external cargo capacity at J4!) the larger upscale is even more advantageously positioned to exploit arbitrage opportunities in speculative cargo by connecting far flung markets to each other. However, the upside is that the larger ship class can be chartered(!), potentially on a long term basis (like a whole year), for 3rd parties to fill the ship's transport capacity and still turn a profit on short range/high cargo volume transport services ... meaning that if an operator "falls on hard times" they at least have the option to essentially contract their transport services to a 3rd party and start making profits again and rebound on their balance sheets back towards being in the black. The biggest challenge would be keeping enough cash reserves available for speculative cargo trading in order to break into wheeling and dealing so as to make it big (and presumably cash out at some point).
However, you don't get that "flexible" option of operations without any external load capacity.
Pretty much all of the LBB2.81 commercial ships feature 1G maneuver drives ... meaning they effectively have no external loading capacity (add tonnage outside the hull and their maneuver drive code turns into "nyuh uh" according to how the RAW works). Starships built to tow external loads will ideally want to have jump, maneuver and power plant drive output numbers that all match in the 2+ range ... which the Scout/Courier (ironically) manages to do unintentionally. So a Scout/Courier could potentially transport up to 100 tons externally at J1/M1 (standard A drives at 200 tons yield code: 1 performance), although the ship would need to be modified (slightly) to enable this. I use the small craft berthing cost rule from LBB5.80 to account for this (Cr2000 per ton of capacity needed) ... so adding 100 tons of external load "towing" capacity at J1/M1 to a Scout/Courier would cost MCr0.2 (bargain really...) ... and the ship becomes unstreamlined while encumbered with an external load.
With that approach, you can basically turn a Scout/Courier into a "poor man's Free Trader" (kinda sorta) and have a larger cargo (but smaller passenger) capacity than an actual 200 ton Free Trader (that also uses all standard A drives too). However, without any external load, the Scout/Courier remains a J2/M2 starship ... while the Free Trader without any internal load remains a J1/M1 starship ... so there are some interesting edge cases that this approach to things makes possible. You also wind up with a much more diverse Traveller universe of starships, but that's just a side benefit.
Hope you enjoyed the Wall Of Text™ if you actually read this far.
