Ed -
What I would suggest would be far from practical.
In the perfect world, as before mentioned, a 8' Stainless steel whip (1/4 wavelength) mounted in the center of a solid metal surface of at least 16' would be ideal - unfortunately, though, we don't have that luxury of available height or ground plane.
Unfortunately, the height restrictions and construction of these coaches on;y allow the types of antennas that the manufacturers have been providing. Short antennas that offer no 'gain' at CB frequencies inorder to make the radios operable - not necessarily fully functional.
I have the very same antenna with the Ring(s) on it on my '04 Horizon. My Fleetwood coach and Country Coach and Sportscoach that Ive owned over the years had the very same one.
At best, CB radio will get you about a mile range in the country at 5 watts (input power) and a few blocks in the city. With the congestion of so many people competing for air time all on the same channel, no one can hear one another anyway unless they are close to one another. Regardless.
I used to sell WIlson, and Hustler and Firesticks and all of the other major brands on the market. Unfortunately they all worked about the same. The designs were a litle different, as was the packaging and the advertisement. But they all worked about the same.
By design, center loaded antennas work better than most - like the trucker antennas you see mounted on the mirrors of the big rigs. They DO perform a teeny bit better than the base loaded ones, but still not nearly as good as an 8' whip.
I checked the SWR (VSWR) on mine this afternoon. Resonant frequency is 27.145 Mhz with a 1.9:1 SWR. If I were seriously relying on the CB radio for traffic reports or emergency communication - I would accept the SWR I am measuring.... and still rely on my cell phone.
I know this is probably not what you're hoping to hear - but save your money and hang on to that cute one that came with your coach.
It's as good as it gets.
Ride Safe !