Just to update this, I've now fitted a V2 clutch bell and dust cover
I messed about with various shimming options, all involving putting the shims behind the flywheel collet to avoid messing about with tiny shims around the bearings.
Thought 1mm might be too much, but having tried 0.9mm and found it too loose I've gone back to the original 1mm shim. This is using an Xray flywheel, clutch and bearings.
Xray list various shim widths in the manual to use behind the collet - I only had the 0.2mm thickness ones, so used some others I had from a different clutch system rather than packing out with half a packet of the 0.2mm ones!
Obvious advantages of no crud getting into the bearings, no little shims to lose when you pull the clutch bell off to service, easy to swap clutch bell sizes without needing to re-shim (hopefully!)
Will run it on Sunday at a track I know to be fairly dusty when it's had work done on it to see how it holds up