I have several SWC's (SWC with C lens, SWC/M, 903SWC and 905SWC) which I would like to acquire a accute matte focusing screen for. I think the models I am considering are the newest (41050) and I've read that 41057 with the built in bubble also works. Is this true as locating a 41050 is difficult? Also, I just purchased a RMFx reflex viewfinder to use with the focus screen adapter which I hope to find. Can I use this viewfinder with all the SWC models and either the 41050 or 41057?