Thanks for all the great suggestions. Andy, I especially liked the idea about moving the stand over to the opposite side of the court. I'll keep that in mind. Jan and Felix, I sure wish I had guys like you around here to pester with questions. I'll try to start weaning myself from my reliance on line-up tracking aids!
Jan, before the match even started I explained to the coaches that I would do the best job that I could but that it was highly possible that I might miss calls having only one set of eyes watching the play. The home team coach was very laid back and I had no problems with him before, during, or after the match. The visiting team coach was upset by a couple of calls/non-calls, but didn't cause any problems. I didn't get any feedback from anyone other than the AD, who said I did a great job (but I took that with a grain of salt since he's a basketball coach who doesn't know anything about volleyball).
Have a 6th grade match in a few hours. Those are always a lot of fun!