I haven't actually tried this so it's strictly fantasy at the moment. but the idea is to encase the power antenna in gray pvc pipe with a cap at the bottom and floor flange or similar item at the top to facilitate mounting it to the fender. maybe the fender mount is threaded, this could require a male and female coupling, so the pipe sheath can be easily removed. the gray pipe is less rigid and less prone to cracking than the white plumbing type. black ABS pipe could be used as well.