People seem to be getting good results with just the manufacture recommended mix of 209. Then again it is a bit of a ghetto solution for people needing a flat edge when they don't already have one and are unwilling to spend hundreds/thousands to get a straight edge.

Not a case of being unwilling to spend the money required to get a level surface, I simply don't have hundreds/thousands of pounds so the options are more limited. Now I have something else to explore having read your last post DC thanks !!
Don't know why I didn't think of it myself, one of my customers has a business grinding optical lenses amongst other things, They bought some machinery from a liquidation auction a year or so ago that I think is just in storage in case their own machines have problems. But if any of them are hooked up & I ask very nicely there is a chance that they might let me use one of them, sure there must be something I could offer to do for them in return.