:) I wrote "heavy" and 40-60 lb mono-filament is damned hard to stretch and I assumed when I wrote it that the individuals who measure and calibrate wheelbase would have greater than a double digit I.Q.
The "problem" with metal wire is that it sags, kinks, and misbehaves.
Use heavy mono-filament and misconduct great enough to cause stretching will pull an arm out of it's socket.
EDIT EDIT EDIT
Spectra is GREAT, but rather inconvenient to find unless ordered online. Thank you for mentioning it. It would be a great improvement.