I use a large (Kilty) bag with not a lot of packing in it. I like this because when I sit on it my bum is basically on the floor, and what packing is in there forms a donut around me for a very stable sitting position. I like this size bag, but from reading the comments here, it mostly comes down to the size of the bag, and the larger bags being used in an incorrect and unsporting manner to gain an advantage when kneeling. I don't know exactly how long the larger bags have been around, I'm sure some were in use when I packed in FT in September 2008. The rules limit the thickness of the bag, so why can't it rule on the overall diameter of the bag: IE: no large bags. This would be a step down for me for reasons stated above. The smaller bag could not be used in the way the larger bags are to gain the advantage. I have tried some kneeling positions in the garden, and to my surprise I found that kneeling on a piece of carpet was just as good as my bag. So a 1CM thick piece of matting placed on every kneeling lane would suit me.
How about someone trialling a kneeling mat at a shoot. Just put 2 target on a lane which is not part of the course and invite shooters to "have a go" .
The Pope HW97 V-Mach. Gary Cane Laminate stock. Leupold Competition 40 mag Mildot.
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Pro-Sport. Warren Edwards Blue Laminate stock. Bushy 8-32x40.