This would almost seem to contradict the view on the size of the mat or carpet allowed:
F2.19. Any number and type of object(s) (of any material) may be placed beneath each rest to
compensate for variations in the height, slope or surface of the firing point, also beneath and
around any rear sandbag or beanbag to reduce its rolling, but such objects may not touch the
rifle fore-end or butt.
Maybe the DCRA or US rules are different...
F2.19. Any number and type of object(s) (of any material) may be placed beneath each rest to
compensate for variations in the height, slope or surface of the firing point, also beneath and
around any rear sandbag or beanbag to reduce its rolling, but such objects may not touch the
rifle fore-end or butt.
Maybe the DCRA or US rules are different...