Arbortech mini carver and saburrtooth carving disk

Hi. I have just got a 2inch saburrtooth carving disk for my arbortech mini carver and wanted to make sure I’m not doing something wrong…

When I put the disk onto the unit the existing spacer sits higher then the saburrtooth disk so the screw won’t tighten onto the disk. You do get a spacer with the arbortech that you can out above the saburrtooth and that seems to work but I though that was for more clearance from the guard.

Any thoughts? Cheers