I think we can officially clock in robkelk's stripped-down speedsters, at .2c, as "fastest speed achievable with a speed drive".
The sister "deluxe" models, at .18c, hit the mark as the fastest speed achievable with a speed drive in a ship that a standard-model human can ride for any length of time.
The sister "deluxe" models, at .18c, hit the mark as the fastest speed achievable with a speed drive in a ship that a standard-model human can ride for any length of time.