Palm rests aren't permitted on 10m air rifle. These are an accessory for 0.22 rifles. You can add wood (or card/paper)to build up the fore-end to the maximum depth (80mm from the bore-line from memory).

Some of the modern alu stocks blur the line, with wooden blocks fitted to the metal skeleton chassis.

This is a palm rest: http://www.edinkillie.co.uk/ecatalog...ml?cPath=11_15