Another thing Cam, don't always use the biggest transports. You know how much fun it is to fly a smaller one compared to flying a bigger one? Much more.
Trust me, i have 6 ships i use exclusively for trading, and only 2 of them have 5000 cargo units. The others range between 500 to 4200.
It's also a nice thing if you can switch between your trading ships if you get bored on one route. Say you have a Republican char, get bored of that route and switch to your Kishiro ship. When you get bored again, you switch to your little Bactrian and do a run from Niverton to Malta and back.
Of course, some people might ask, why the hell do you need more than 2 traders?
Just for fun and entertainment. All of my traders have totally different routes. Maybe two or three systems are the same, but non of my traders docks on a base another of my traders docks.
In a brilliant tactical movement, i charged backwards.