How big is the ship it's on? If you have a 10. 2 k ton jump drive on a 2k ton ship, you can only ferry through 2k ton ships. Or, more clearly, max size for accompanying ships is the size of the jump tender ship, not the jump drive on that ship.
If the tender's size is deciding factor, then my tenders are too small, my military tender is only 6 500 tons. Now I need to decide what I want to put in them. I have couple designs I'm in need of, and both could be incorporated to tender design. Back to furiously designing fleet composition it seems!