Thanks for the suggestions, gentlemen.

Fuel - 10% NM; 18% oil (syn:castor blend); plug is an OS #8; original glow plug with probably 4-5 running hours on it. I have not had to change out the glow plug. The fuel tank is about 6" aft of the firewall. I have actually held the plane vertically (worried about just what gaRCfield implies) to be sure that it was not leaning out too much in flight.

I tried to keep the cowl clean externally, so only have a 1/2" hole over the cylinder head for glow driver access. I could open the cowl over the head more, but was trying to avoid that if I could.

I put in a small baffle plate below the starboard air inlet to keep cooling air flowing up over the cylinder fins; prior to that, air COULD have moved directly from the starboard inlet, below the crankcase, and out the vent. A small baffle now forces the air up over the cylinder. Several have suggested that I close off the port inlet (away from the cylinder), and that is an easy mod I can make. Might try opening the HS needle a bit more also, but I have found that this engine/prop combination slows quite a bit if the mixture is too rich.

I have the muffler mounted using the 90* adapter, so it sits transversely, partially in the open airstream, and at the front of the vent opening on the bottom of the cowl (I know, a pic would be way better). The muffler is essentially directly below the crankcase.

I'll take some pics tonight and post them later.

I appreciate the advice. Thanks again.