There was a really distant binary that I wanted to explore, for completeness, and I came up with an abusive way to get there.
Ingrediants:
2 ships with 1 size 50 HS maximum boosted engine, tractor, large fuel tank, enough engineering systems to fix an engine mishap.
1 commercial ship with large fuel tank and tractor
1 carrier, large enough to hold the aforementioned tugs, no engines, lots of engineering systems, and a tractor
1 commercial jump drive ship, tractor, and lots of fuel tanks, big enough to jump the carrier.
I call it a push me-pull you.
One military tug is always in the carrier, not advancing its maintenance clock. It tugs the commercial relay tug, so you have a tug pair of roughly 100 HS (80 HS military tug, 20 HS relay tug) setting the speed of the whole squadron.
I figure you could get this to about 15k with magnetoplasma, maybe a bit higher. You could theoretically move a whole fleet of commercial engined or engineless ships this way, if every component has a tractor. It is silly, and cheating, but I thought it was an amusing idea.