Larry,
With the ceramic and ABC setup you can run them down at 25% total oil (also works OK for the original steel/iron). I have had slight crackling (pre ignition) with high oil % 27-29 (it raises the compression). Once I drop to 25% (50/50 castor.klotz) the crackling was gone and it had a very solid run. I would add 3 oz of Klotz to your 22% GMA.
If you are going to run them with a muffler don't load them with a 10x6 prop, use a 9x6 (open face the 10x6 is OK). Also, if you are using aluminum pads on the motor mounts make sure you put 1/32" plywood crush pads under the motor case lugs to allow the mount to be solid and allow for the lug casting relief angle.
Best, DennisT