Hi All,
This is what I am doing now with my McCoy 40. It has had the piston/jug heat treated to help it last longer while using a muffler.
PA NVA
10-6 Rev Up EW prop
Thunderbolt plug
Sig 10%-25% all castor with 4 oz. castor added.
Adapter to bolt ST 46 mufflers to the hole in the exhaust port center.
Great 4-2 and easy to set. It pulls the Parrott P-47 real easy!