Hi Joe,
I'm using the Nanco's on a Model III with wooden strut fairings. They're wide, but I don't have any clearance issues. I've had good luck with them both on grass and pavement.
There are many sellers. Either look on Ebay or Google "Nanco N800 Slick" and you should find them. You might want to verify the date code with the seller. Mine turned out to be old stock although it hasn't caused me any trouble.
You might look over this old thread as well: http://www.teamkitfox.com/Forums/sho...ighlight=Nanco