Prop size for this engine should be something like a 13-6 or 14-6, the heavier, the better. Master Airscrew or APC come to mind.

Remember, this procedure is based on your engine having an air bleed screw, not a low speed mixture screw. Same basic principles, different applications.

Air bleed adjusts air into carb at idle. Low spped mixture screw regulates fuel into carb at idle.

First set the high speed needle for a "full RPM minus a few hundred" speed.

With the engine running at as low an idle you can get, and the glow plug battery connected, do the "pinch test".

Pinch the fuel tube from the tank to the carb tightly and listen to the engine. If it speeds up, it's too rich. Open the air bleed screw a bit and try again.

if it immediately slows and dies, it's too lean. Close the air bleed a bit and try again.

Once the approximate setting is found, try letting the engine sit at idle with no glow battery for several minutes. Then briskly open the throttle. The engine should increase speed with no spitting or sputtering. If it coughs and blows a lot of smoke, it's still too rich. Open the air bleed a tiny bit.

If it hesitates and sags, it's too lean. Close the air bleed a tiny bit.

A good idle speed for this engine would be in the 2000 - 2200 RPM range, all day long.