I just bought a used Saito 1.20 off of Ebay ($165).  Supposidaly almost new. What size 3 bladed prop should I start with?  I plan to use the engine on a rather large Extra 300S scale aircraft.  Also what plug works best?  By the way the new Saito around this size is a 1.25.  I beleive not legal for control-line flying by 0.05?