I have a 590A1 with an 18.5" barrel and want to install a light on it. I am looking for some type of clamp to mount the light. I already have a light with a rail mount attached to it. I need a 3 slot picatinney rail to attach the light mount. I bought one of these and it was too long http://www.cheaperthandirt.com/ItemDetail.aspx?sku=SHT-071 I saw this mount at CDM and it looks interesting but I don't know if it will fit The mount is here http://www.cdmgear.com/bmt.html A picture showing the mount with a 3 slot rail is here http://www.cdmgear.com/mossberg.html There is only about 3/4" free space between the barrel screwdownthingy and the slide handle (see attached picture). I've looked for an extension to install on this weapon that would lengthen the mag tube but have not found one that fits on the 590A1 (that's a whole 'nother thread and promises of deliveries after money changed hands so let's not go there in this message). Anyone have any solutions for this?