A couple notes on balancing. Props tend to have a little flashing at the edges of the center hole. If the prop has been reamed, the flashing may be more pronounced. The flashing (rough edge) will not let the cone of the balancer to set true to the hole and it will give you a false balance.

To correct this, you need a stepped prop reamer. Ream the prop to the proper size hole, then do a 1 turn cut with slight pressure with the next step. This will cut the flashing off and leave you with a very slight bevel on the edge. Do this on both sides of the prop. This will give your cones the best chance of setting true to the bore of the prop.

Second, when you install the cones and shaft on the prop, spin each cone a couple times to make sure any dust or stray balsa chips are not interfering with the seting of the cone. Keep the cone clean, wipe them down with a rag with solivent once in a while. If you can see anything on the cone, it is to dirty to do it job correctly.

A lot of times, you will find a prop balances tip to tip, but has a heavy side. IE once it is balanced, turn the prop 1/2 turn and see what happens then. If it stays in place, you are good to go, if it roll 1/2 turn then settles down to a balance, you have a heavy top/bottom and it needs to be resolved. One of the old timers at our field skuffs up the hub of the prop on the light side and applys a ribbon of epoxy on the hub. Leave it hanging with the epoxy hanging down so it forms a nice bead. Use more than enough to do the job. Then when the epoxy is set up, you can grind off the excess to balance top to bottom.

One other note on reaming. The APC props have a stepped bore. Make sure you start the ream from the large side. This keeps the pilot of the reamer tracking the orginal bore. If you start the reamer from the small side, you will loose alignment about 1/2 way through the prop and it is easy to get an egg shaped hole due to the wobble of the reamer. The best approach is to ream the prop on a drill press with a setup that keeps the hub exactly alligned with the reamer. IE you don't wnat the prop setting at an angle, but exactly perpenducliar to the axis of the reamer, in all directions. I found my big drill press's table was off by about 1/4 degree and I was getting wobbly props. My small drill press is dead on, and that is the one you want to use. I also don't turn the drill press on, but hand turn the drive pully, watching to keep your fingers out of the belt. If a reamer isn't turning exactly true, you will get an oversized hole under power, but driving it my hand lets it follow straight.

Don

Edit. I had to add one more thing, NEVER drill a prop. You can't get a drill to follow the hole with any accuracy. The stepped reamer is the only way to go