I started my LF study and gained knowledge from here. To my personal requirement I eventually ended up with a VH-R which I am really happy with. The question is that I want add a Polaroid back for it, but I do not know how the back works to gether with other accessories, such as the G spacer, RF spacer and the special g roundglass fram/back, to correct the film plane. I bought a Polaroid Back at a v ery good price and want add the accessory(ies) to make it a go. I guess the RF s pacer is for correction of rangerfinder and special groundglass back is for corr ection of focus at backwarded film plane. What is the G spacer for and where it should be placed to make a correction. If you am not using RF, does the G spacer alone do it well? I have the Horseman manual which is helpless in this respect. Thanks for your help!