RE: HOB Messerschmidt 109..propping Cox .051 R/C
I tend to choose a prop that fits the plane, then put a motor behind the prop that will spin it. In this case you have a motor that will do fine with a 5X3 to a 6X3, So I'm with CP on this one. Try all 3. That being said, I find warbirds, or anything with a high wing loading need thrust more than speed, but you need enough speed to keep it airborne. My gut says the 5.7X3 is the ticket.