8spd cassette onto a 10spd wheel conundrum...

Ok, appreciating it's a bit weird / retrograding, but I've a NOS 8spd Campag block to go with the Mirage gruppo and because I'm a skinflint I want to use my second-hand Fulcrums. With a 10spd hub.
The 8spd cogs fit (they have the same single-small sprocket) but when I drop them on, obviously it's short of the spline's overall length, with the result that even with the screw-top threaded down it's not locking the sprockets down.
So the first question is, is there some kind of spacers / shims to tackle this problem?
The second is that the lockring on the 8spd is bigger that the 10, so doesn't fit the hub. The 10 is a smaller diameter so am worried it's not going to lock the cogs properly. Should I worry?

Well, sort of made it work - in principle.
Added a c.2mm wide spacer between the last cog and the locknut. It's finished black so could do with a silver one, and slightly wider (it's a Shimano fitting that the LBS had foc) so I can put it over the hub, behind the first cog.
Is this a safe / reasonably sensible thing to do? Everything indexing properly and appears aligned...