Ski, when I convert engines to Diesel I use a three blade prop with the same pitch and diameter as the recommended two blade for glow operation. An example, my Fox .74 turns a Graupner 12x8 two blade at 11,200 rpm as a glow on 5% nitro, converted to a Diesel it turns a Graupner 12x8 three blade at 9,400, I've not tried the 12x8 three blade on the .74 on glow fuel.