I didnt read all the long posts but your 800 lap time should be determined on your 400 time. All of you are just guessing and not using other distances ran to determine it. In a conditioned/veteran athletes you should go through at 400 time + 4 seconds......as a younger less experienced racer I would go 400 + 6 seconds.
What is your 400 time? That should be end of the thread.
Let me quote myself since most of you arent listening.