For my league we have a ratio of starters to Bench players that roughly equals that of the NFL. Ours is 9 starters/7 bench, or just slightly under half as many bench as starters.
For your league I'd recommend adding the ninth bench spot to balance things out.
Peacesells wrote:8 spots look like enough. Why do you have to draft an even # of rounds?
Especially if you're doing a Snake you want an even number so the "weight" of the draft balances out. With an odd number of rounds you end up with one side of your draft having more early-round picks. With an even number that balances out, with the first guy drafting also drafting last, the second guy drafting second to last, and so on.
If you're doing a Straight draft the number of rounds is really irrelevant.