I found that 800s arent too bad. If you start at the 500 mark, then you just do one lap and end 8m past the 200 mark (who is roughly where the door is after the sprint area). If you don't feel like jogging back to 500 then you start at 300 and finish just past 0.
The only disadvantage with this approach is that you don't have good pacing information, since the lines come at odd distances (except for the first 200 when starting at 300).
Ah, yeah that works pretty well. As long as I have feedback at one lap and for the total then it's ok. After that I can compare times at other points based on previous reps. Plus this approach means you finish right after a downhill. ;-)