This is from Circle fly.
http://www.circlefly.com/html/bp_cartridges.html The wads and cards I use with great success:
The overshot will need to be glued in place and we recommend using Duco cement, paraffin, waterglass, etc. to hold the card in place. Another glue worthy of use is arrow fletching cement, such as Fletch-Tite brand. It is made to stick to non porous surfaces and dries quickly. I recommend using one size larger overshot card in extruded brass. For example, in a 12ga. thinwall shell, use 11ga nitro and fiber wads, and use a 10 ga. overshot that is glued in place. This will help insure that your load column is not going to move.