[dataweaver]

You might also want to go with a tidal-force-limited boost drive, on the principle that tidal forces are unique to actual gravity and completely absent from the likes of spin gravity and acceleration gravity. Where gravity falls off with the inverse square of distance, today forces fall off much more quickly, with the inverse cube of distance. Since Jupiter has about a thousand Earth-Masses and Sol has about a thousand Jupiter Masses, their respective today force ranges will be ten and a hundred times Earth's today force range: that is, you'll feel the same tidal forces roughly ten times as far from Jupiter or a hundred times as far from Sol as the distance from Earth that you'd experience the same tidal forces. Conversely, an object with a millionth of Earth's mass produces comparable tidal forces at a hundredth of the distance; so even starships are likely to produce significant tidal forces.

The nature of the limit could be a matter of speed (the more tidal forces there are, the less of a boost you get), or it could be an engineering issue (the amount of tidal forces the boost drive's systems can cope with depends on how well they're engineered, resulting in boost drives being rated for how close they can get to large masses and still operate).