A lot depends on the type flying you do, as well as the plane.   The early days when 1/2A was all I could afford, I used the 6-4 top flite props or even the Grish.  The 6-3's  did not have enough pull for me.  I flew off an old discarded table with my stooge I made in the back yard where we lived.  Most people now a days like to hear the engines turn up rpm's and run 5 to 5 1/2 inch props of varying pitches.  The joy of modle planes is trial and error.

             One other thing to keep in mind is that not all engines came with the same  porting. I have several Golden Bees  with the standard#2 Bee cylinder and several others with the dual port #1. In addition I've found this to be true with some  of my Babe Bees as well. The 1980's Babe Bee's came equipped with dual ported Sure Start cylinders. Not this this is going to have an extreme effect, its just might enable you to use larger props. I do prefer to let them run up by using 5x3 props but going back I was using Top Flite nylon 6x3's all the time with good success. I found the APC 5x3's to work exceptionally well but they do come with a bit of a price. I typically pay around 3.95 for them. You do need to make a bushing out of aluminum or fuel tubing due to the large hole in the prop. The other problem is they do break easy if it strikes the ground on landing. If APC stops making these smaller props were in trouble. They're really the only one left making the small stuff. Tornado had a terrific line of the white props as they were extremely duarable and they worked well. Its just that these are somewhat tough to find today as well. Ken

Ken,

Try Sam's Stuff & Hobbies:

http://www.sshobbies.com/

APC props in that size range are typically $1.60 each. Don't hesitate to call about sizes they don't show, as they will order ones they don't stock.

Wonderful people to deal with, and full supporters of control line flying.

Bill

My problem with prop choice seems to be the ability of the engine to handle the load through a complete competition pattern.  As such, our gang is hovering around the APC 5.5x2, 5.7x3, 6x2 props to unload the engines enough to not overheat in the full pattern.  We are NOT sport flying, so continuous, though lesser power is vital.  If you want to scream around sport stunts for 3 or 4 minutes, that offers a great deal more lee-way.  We need reliability, consistency and repeatability.  It took me a few years to understand the difference between the Cox tuning and the more modern engines.  Cost me a few models, too!  In sport flying, if your engine run goes south, you just fly level, in competition, you LOSE!