I'm having issues aswell.
1) I placed the sd2vita.skprx in ur0:/tai and placed the line under the Kernel in ur0:tai/config.txt
2) Copied all the files (hidden ones aswell) from my ux0 memory card to the microSD.
3) Deleted ux0:tai/config.txt
When I open vitashell and mount the gamecard, it tells me it has been mounted but it doesn't show up. Any help is apreciated.