Re: Prop Balancing
In general the scotch tape should work fine but it is not the most durable one. In hot weather, the lower quality tape may shift or even come off because the glue starts to melt. If the blades are off so much so that you have to use a large piece of tape, say over 30% of the blade, then you want to make sure that the tape has no bubbles underneath. Or you can go for the thicker tapes.
As for where to stick the tape on the blades, I prefer to use narrow width with the length that is long enough to wrap "around" both top and bottom of the blade, starting from the leading edge then go on the TOP to the trailing edge and come back UNDER the blade until it overlap the beginning on the TOP somewhere. This way you have a close loop of tape with the end facing away from the moving air and since it is thin and long, you are disturbing the air foil profile as less as possible.
I don't sand off or remove the material from the heavy side of the thin blades but build up the weight on the lighter side, either by brush on paint or spray paint and let dry and check the balance again.
New after market carbon fiber props for the Phantom came pretty close to perfectly balanced. I bought several sets and most of them 3 out of 4 needed no balancing at all while the others only needed a few strokes of sanding.