Due to the trade fleet bug, big trading fleets might not be optimal. The amount a fleet keeps when it returns to the home planet seems to be fixed, not dependent on the size of the fleet. The end result is large fleets (like my fleets of 100-500 bulkfreighters) can't afford to fill their holds after returning to the home planet, and need to make some good trades to get to that point. Smaller fleets (I think < 10 or something) don't suffer from this.
The bug actually affected any fleet with 5 or more merchants (or bulkfreighters).... and GOOD NEWS, Dave just fixed the bug last night. Your larger merchant fleets won't get their full starting money until after they return home though.
