Everybody is different. I have seen guys with 2.75" of arrow in front of their rest and I have seen 1/8" of arrow in front of their rests. 1" is a good place to start but you could certainly go shorter if you want to.

I highly suggest downloading the On Target 2 software. It is free during the trial period and you can input every little thing about your setup. It will tell you what arrows, length, etc. to purchase to optimize your rig.

Best of Luck!