SWEET
Just my stupidity showing but why would bronze be best ??

stirlingmac,
I actually used bronze thrust washers with my allow rocker spacers. I didnt go into it in the other thread because I was trying to keep my explanations simple. Fitted them wherever a rocker egde came directly in contact with any post edges, I did this just incase but in theory the alloy should be OK because if the rocker to valve stem alignment is right and the oil clearance end floats set properly, Bronze shouldnt be needed. Plus of course it's a little heavier than T6061 - every little bit matters

So what's your recommended clearance?

Set all end floats to 0.003" (hot) to keep everything wet whilst still locating the rocker axis centrally over the centreline of the valve stem.

I thought the idea behind these bushes was to prevent the standard springs from compressing, and bending the pushrods through the rocker arms migrating along the shaft.

No dissadvantages with this modification. There is no noticable noise especially considering they are most useful in very high rpm applications.