You can figure about 1 jet size per 2000 ft. My whole point is that leaning the intermediates will lean it at WOT as well, I would rather have him start rich at WOT and lean it to suit. You can be pretty lean at part throttle an not hurt anything, just don't want to be too lean at WOT. MPH and plugs will tell you where it wants to be with the final jetting.
As far as the 2 circuit, I think by far it is the best way to go and is not as difficult as you might think to make the change. If you get to that point I can lead you to the info to take it on yourself as long as you can handle a tap. Let me know how it goes.