Hey Sandog,
Did you run the usbmcinstaller to disable the 3g error message? You want to run that program once to disable the 3g error message, then don't run it again to set up the mount points, you just need to delete the usbmcplugin.skprx in ur0/tai and remove the line from the config.txt in the same folder.
Then either download/install autoplugin app and set up storage manager in there = easy mode
or download storage manager plugin and edit the storage manager config file manually as mine is shown below:
MCD=grw0
INT=imc0
GCD=uma0
UMA=ux0
Then reboot and should be all sorted.
You can also change the settings in adrenaline to load games from the uma0 once set up
Edit, sorry just read your earlier post you had setup storage manager correctly when you were on 3.70, what's the issue you are getting?