I have now got a friend interested in a 460 but he has a FAC, we have been discussing how to tune it we also have the help of a RFD and custom part designer.
So far suggested is a 30 coil .150 high power spring with a custom made to fit steel guide and perhaps some weight in the piston, has any one tyred something like this combination?
Barry.g

In my experience, the 460 is hard on the plastic guides. I think the custom fit steel guide is a good idea. I have only brief experience with the Maccari 48/52 spring, but I would think that is the way to go if you are not using the stock spring.