Well, I finally sat down yesterday and looked at the Honda filter and what has to be done.
Yes you need to make up the 8mm thick spacer to go on top of the Honda fliter and I have machined a recess in the spacer to take an O ring to stop any leakage.
However when looking down the inside of the bolt, I noticed that the rubber seal blocks off most of the four holes for the oil to flow through at the threaded end. Not wanting to restrict oil flow in any way, I drilled 4 extra holes lower down the bolt.
The bike would appear to run well. The Honda filter was GBP5.00 and came in a nice sealed bag, so I know it was clean.
Job well done, if anyone wants photos, etc e-mail me off line [email protected]