When attaching a string to a French Plumb Bob, Do you tie the string around the center whole so that you can SIGHT directly through the center whole, or do you put the string right through the center whole? -Collin
"The lyf so short, the craft so long to lerne." Geoffrey Chaucer (1343-1400)
You may find it useful to add a small bead just above the knot, often the hole in the wire frame is larger than an easily tied knot and a bead will stop it all slipping through. I have the cord from a Veritas "flat bob" on mine; being black it works well but best of all it is fine braided line and the spin is minimal. I'd be keen to find some similar line if anyone knows a good source?
For a relatively fine woven line, Mason's twine is probably the most economical and available solution. It usually comes in a variety of high visibility colors. If you want to go for something finer gauge then try looking for performance kite string. A round braided kite line is 30-50% lighter and finer than an equal strength mason's twine.