Personally I don't have player ships exceeding the tonnage of ship they can muster out with. Beyond 400 DTons you don't need to make the compromises that prevent it becoming a money making machine and making adventure unnecessary.
Running a 100 Dton ship for trade is hard work so it is mostly a vehicle to travel to paid adventure that can subsidise some of the running costs.
Running a 200 DTon trader can be credibly profitable and you can take adventures that interest you and just run trade while recuperating.
Running a 400 Dton ship can make so much money in trade that adventures become an overall cost unless the rewards for adventure are out of vastly proportion to normal wages. That means you are no longer running small side jobs and are starting to conduct campaign changing activity.
Once you can afford a ship over 400 DTons you have "won". Your ship is worth upward of MCr100. Even if you don't own it outright your have still been able to convince someone to loan you that amount of money and your prestige will be commensurate. Your other equipment will be at system governor's resource level. You have the money to afford most equipment (like battledress) and the sort of clout to get permission to buy it at will (or you will just shop elsewhere). Your ship could be generating KCr50-100 per month above operating costs at even freight rates, if you have a broker you could be bringing in double that by investing in speculative cargos*. That is a new set of battledress every month. It becomes harder for larger trade ships to clear the overheads under the player trade rules as the cargos and passengers become too scarce to fill the larger revenue generating capacities required.
If instead you optimise a larger than 400 DTon ship for combat you become peer level with system defence vessels and the smaller naval military vessels or privateers. More than 4 hard points starts to mean your firepower can be significant in system level actions. You also probably wont make the mistake of under armouring your ship and will likely be more effective than your tonnage suggests.
This assumes CRB/HG style ships. We have had discussions elsewhere that the military vessels are not optimised. Traders are also not necessarily targeted at the highest profit point. Things like liners and merc cruisers are out of scope for player groups as they will require large NPC crews (and unless you go droid heavy that is a lot of work for the referee).
It will of course depend on the campaign, but once you are able to sustain yourself above the 400 DTon level the majority of published "adventures" cease being a challenge. Some of the published adventures offer a rags to riches arc where by the end of it half a dozen sessions you command or own a 1000 DTon plus ship. I find it hard to see where a referee can go after that as the next adventure will need to be at the sector influencing level. My feeling is that beyond this point the return on the referee investment diminishes. Either the power or the number of adversaries needs to increase to retain the challenge and that is more work for the referee and rolling 100 skill checks in combat is no more diverting than rolling 20. The sad alternative is to take it away somehow but that just becomes dispiriting for players. Most would prefer a gradual improvement rather than boom and bust.
A small skirmish action between half a dozen characters and an equivalent number of peer level opponents is far more immersive than an assault against dozens of mooks leading to a confrontation with the "end of level boss". It all becomes a bit digital, it is hard to get a marginal victory or defeat, it is also far more work for the referee. It also makes little sense to pay a small group of mercs KCr100's per month (which is what they are giving up by working instead of trading). If you are fighting a similar peer level small group of adversaries again why would they bother risking their life when they could just run trade. That means the pay out needs to be moving in the direction of MCr per month. Those are company to regiment level pay bills.
*If you have KCr1 per month of disposable income there are few cargos you can actually afford to invest in. The return on the investment from those low value cargos once you take off the lost revenue from shipping freight is slight. Speculative trade is a useful bonus, but also a bit of a gamble. Once you can buy cargo that costs KCr10's per ton the profit margin increases significantly even with the same percentage on the base price as you are still only losing 1 DTon of freight revenue.
You can afford to have a more expensive cargo sitting in your hold for a few jumps in order to get a good price. You can also wait and only buy when goods are very cheap as freight alone is clearing your costs. That moves your margins from Cr10s per Dton to KCrs per DTon and makes getting a profit far more likely in general. Once you can guarantee a profit of even 10% on an overall transaction, speculation in KCr10 per DTon cargos becomes a default decision. Once you can afford the occasional cheap DTon of pharmaceuticals it becomes a magic money tree as you can hold that cargo for years waiting for the right market before it becomes a loss maker. At this point your opportunity costs are the profits from other speculation rather than freight and you will be turning over MCr per month.