Hey I am in the air bag business, and we do a lot of cantilevers. The reason people say they ride nice, is because the increased leverage softens a stiff bag. What that means exactly is that people like to use a 224c ( 2600 # ) size bag and put it on the rear. If you consider that is the bag used on the front of a fullsize truck, it make sense that that bag has way to high of a spring rate for the rear. So instead of getting a bag with the proper weight, they move the bags up on the bars. As the leverage on the bag increases, the weight it sees ( spring rate required ) is increased in direct proportion to the leverage. A set up with 2:1 leverage, needs a spring rate twice as high as a 1:1. I would look into getting a set of firestone F9000, 9001, or 9002 bags. Or possibly even air ride tech's 9100's. They will give you the same good ride, and good lift. And not require the massive lower bars needed to support the bags on the bars.
Oh... and that isn't a true cantilever. It is just a lever. A true canti has a rocker to change direction, kinda like an indy car.