Aluminum tape sounds like a not bad idea, I'll have to try that sometime. With the solder, I stick it to the prop with a bit of masking tape to hold it in position. When I get the right amount of lead, I put it on the anvil part of my shop vise, give it a quick blast with a torch and it melts up into a little ball. I pound the ball flat to give me plenty of sticking area and then either a dab of hot melt glue or epoxy. I nip off a bit from my flat piece to compensate for the weight of the glue. Usually my ballast pounds out to about the area of a dime up to maybe a quarter.