you need it to be about 12 to 15cms thick depending on your grain size. the smaller the grain the shallower the DSB can be. Is it possible to get som more glass? or stick a strip there to increase its height a bit?sorry a bit to late orady cut the glass and don't have any 5mm left only 10mm and I cant cut it. Can i make the DSB 5-9 cm or do it have to be 15cm ?