[Irish Wolf]

A reasonable speed for a small privately-owned interstellar craft of the era (like, say, the ship Harry Mudd and his, er, ladies were in when they needed rescue) would probably be about warp 4 or 5. The private cargo-haulers of a century earlier, after all, ran at a little over warp 2, while the NX-01's breakthrough engine design could manage warp 5 at top speed, so imagining the cargo ships of the early 2260s as running about what the old NX-class could do in the 2150s isn't unreasonable in my opinion.