Good point. Going from 0.8c to 0 in a stopping distance of a few hundred AU... the deceleration forces alone would probably kill you.
You’d want to keep the acceleration/deceleration at or below 1g if humans were aboard, especially for the length of time it takes to go to and from 0.8 light speed. To get there at 1g, it would take 283 days, and covering a distance of 19,600 AU’s (0.31 ly). Double that for the deceleration leg. But where does a spaceship get the energy to do this, keeping in mind that the more fuel you’re carrying, the heavier and slower your spaceship will be? I can’t imagine doing it with anything less than some futuristic super fuel like antimatter.