I would want to use a native macro lens instead of adapting just for ease, which leaves the 120. Don't go past 1:2 with tubes though because the lenses fall apart optically.
Seems like you have some nice equipment though so if you can, you'll save a lot of time and futzing if you just get a Imacon or pro flatbed. You could scan a lotta sheets with an IQSmart2. The scans will be easier to produce and better in every way. I personally invested a lot of time and money into serious camera scanning and I believe the technology is promising, but for sheet film there were insurmountable problems. Light even-ness, geometric distortion, and flaring around the edges of the sheet namely. I got an Eversmart Supreme II and within a few months I've sold off all my camera scanning stuff save the light, which I plan to list shortly. Real pro scanners are just incredible.