Don't make it any shorter than 20 ft. Dave. When you play on a big stage one day, you may be that far from your amp! In big clubs like Wild Bills and Billy Bobs Ft. Worth I like it farther away! Just my 2 cents..
Thanks for the replies. The reverb connection is driven by a 1K ohm impedance, so I'll do a frequency sweep on the cable for that conductor with that impedance to be sure the bandwidth is still acceptable for a 20 ft. length. I just didn't want to make it shorter than the factory original.