I made my aileron counterweights from 1″ OD DOM steel tubing. I figured out the wall thickness (.188) that would give me the approximate weight I needed at 40″ length. I drilled and tapped the ends for 1/2 NPT which I will put plastic plugs in once they are permanently installed.
Once the ailerons are covered and painted, I will add a small amount of lead for a perfect balance and cap the ends. I drilled and tapped the tubes to take 4 8-32 screws which will hold them in place.
I ended up turning them down by about 20 thousands to make it easier to slide in my 1″ holes on the aileron nose ribs.