Yes... I agree with Piru.
I think you have to create a specific mountlist with LS-120 disk "features" and the device that recognizes the port where your LS-120 unit is connected.
If you use also not-AmigaDOS formatted disks, you'll have to create a second mountlist where you have to add a string with the right filesystem, i.e. CrossDOSFileSystem.
In short,
TRY THIS!
Don't forget to change the device with the one that controls the X-Surk IDE port.
If you put those mountlists in Devs/DosDrivers, they'll be mounted automatically after booting, otherwise you can put them in Storage/DosDrivers and mount manually from the Shell when you need.
Just a question: does the IdeFix "FindDevice" utility recognize your LS-120 unit?
Ciao! :-)
Alex