One of my very first “good” cameras was a Baby Speed Graphic I bought with paper route money when I was about 12. Learned all about sheet film, holders, rangefinders, sportsfinders, focal plane vs leaf shutters, etc with it. The spring back was always a disappointment because I couldn’t use roll film with it (and couldn’t afford a Grafloc back much less a roll film holder!). Your 101mm lens is probably right for your rangefinder, so if you make sure it is calibrated at the film plane, that will take care of focusing (Kalarts are not hard to adjust). Then use the optical or sportsfinder to compose and you are good to go. I have a 2x3 focusing panel for a Grafloc back from a Graflex XL I no longer own if your eBay purchase doesn’t work out. I think I have a roll holder or two as well. I still have the Baby Speed with a nice 101mm Ektar and picked up a Century body for the Grafloc back. One of these days I’ll put them together. Have fun! (Btw, that is a Galvin 2x3 monorail linked to above. I had one and it worked pretty well with a roll film back)