I am the happy owner of an Arca-Swiss F-line 4X5 view camera, and purchased the A/S compendium lens hood recently. The compendium has 6" slots on both front an d rear for insertion of filters. I got a couple of A/S filter holders which fit into these slots, but the circular cutout in the middle of the holder is greate r the 4"...the packaging indicates these holders are for 125mm (square) filters. Does anybody know if filter holders for 4" filters are availble for use with t he compendium? Are 125mm filters readily available in the US (or even made any where)? I would like to be able to mount filters in the compendium itself since there is clearly the provision for doing so, and avoid having to use a separate, lens-mounted holder, which could possibly be a source of vibration as well as a bit of a hassle to use. Thank you for your help.