I pulled the foam collars off of the cones on my Aries II, screwed the cones to the bottom of the plinth, and level the tt with the feet on the maple board that the tt sits on. Works for me, and cost nothing.
If you want to use the stock feet to level the tt, screw the proper size nut onto the threaded shaft of each cone. When through leveling, snug the nuts tight to the bottom of the plinth with an open-end wrench. This will keep the cones from 'rattling'.
In short, though I've never used the new VPI feet, I'd guess that you'd get a much more cost effective benefit by tuning the cone feet that you have now, and perhaps using the 300 bucks towards a good sub-plinth.
If you want to use the stock feet to level the tt, screw the proper size nut onto the threaded shaft of each cone. When through leveling, snug the nuts tight to the bottom of the plinth with an open-end wrench. This will keep the cones from 'rattling'.
In short, though I've never used the new VPI feet, I'd guess that you'd get a much more cost effective benefit by tuning the cone feet that you have now, and perhaps using the 300 bucks towards a good sub-plinth.