I read somewhere that adding a match stick under the rest and side plate would provide cleaner arrow flight. Is this true? Both of my bows have a radius shelf so I was wondering if I could benefit from doing this. I shoot a Kodiak hunter and a howatt hunter.

The smaller the contact point, the less any shooter induced bow torque will effect arrow flight.  So yes it can make a difference, but it may be minimal or not noticed as the fletching corrects it.
 I never used a match stick, but have used part of a toothpick under each.  Especially when shooting off a shelf on bows that do not have much radius to the shelf.

The shelf and side plate on many bows have a radius, so it may not be needed.  It does help however on bows with no radius.  I use a sliver of leather (from and old belt or whatever) if needed for the contact point.

Thanks guys, sounds like it is not needed with a radius shelf. I was just curious about doing this.