what i did was remove the set screw for the antenna then it pulls right outand i used a pair of dykes to cut it to the length i liked my brother in law did the same thing and we havent noticed any radio reception problems either
I did the same thing on my RG. Removed the set screw, pulled the mast and measured from the "ball" down roughly 13-ish inches and cut. Removed any little burrs from the cut and reinserted the mast and tightened the mast down. No loss in signal and the darn thing doesn't hit me in face walking around the back of the scoot anymore. Not to mention it looks much better.
You can get one a stainless one at auto zone cut it to the lenth that you like. File the end down so it fits back into the stock mount and tighten the set screw. Your good to go for under 10.00 bucks
I dont have a RG , I have a08Sg changed mine to a inside fairing mount, now I dont have to wear safety glasses to get into my bags. I thought it was a much better idea than HD's,kinda like my eyes, cant imagine what it would feel like to jamb a antenna wire into them.