Enya literature states 20% Castor. The Enya engines have excellent metallurgy. 29% lube will only slow them down, gum them up and get more slime all over your airplane. I have about 30 Model 5224 engines. I have never run more than 25% Castor oil lube and only when the Nitro is 25% or more. My 1966 29 IV and 35 III have a lot of hours on them. The 29 has been run in a Rat Racer with the 9 to 1 head, #3 Venturi, timed crankcase pressure, and a 7-11 Rev-Up wood prop. The fuel was 25% Nitro and 25% Castor. Even with lean runs that stopped the engine in flight there was never any engine damage. The engine still starts and runs well. The old Fox engines have so-so metalurgy, and small diameter crankshafts, that results in high main bearing loads. The high loads are better supported with the 29% oil. 29% oil in glow fuel is a hell of a lot of oil.
Pat