I am wanting to to transition from the Cokin P resin filters to glass, most likely round filters. (if you think I should do something else let me know). I shoot 95% black and white. Is there any good reason not to do a B60 to 67mm step up ring and purchase the 67mm filters? When I go on the BH website an the proce difference between a Bay 60 and a 67mm Heliopan red filter is almost $80, I have to wonder why. Are they just sticking it to Hassy owners, a supply and demend type thing or somethint else?