yeah 20 is the most I have ever personally gone, and I really didn't want to do that much but had to, it did not cause any problems. As long as it is a good ground it ill be fine that long, But I would suggest around 10-12" for length on ground, that way you can move it around if you get some noise and troubleshoot it a lil' easier. Mine is a little long, I just used the ground wire out of a capacitor kit and they only give you 20" in that kit and I trimmed it so prolly 14" or so.
