Rhop is very cheap. If you would be happier with a easier way Greeny's idea is very simple and somewhat effective. I would also stabilize your inner barrel as madbull barrels like to vibrate. (Very cheap scotch tape teflon tape any thin fillers work.)
When you're shooting your whole gun vibrates. This also includes the inner barrel. The vibration causes the BB to bounce in the barrel more then it should making your shots inconsistent. By stabilizing it the vibration is cut down allowing a smoother BB path.
Rhop is a hopup contact patch that is rounded, and gives a solid contact around the upper part of the BB for a extended period of time over other hopup nubs. This stabilizes the BB and also adds a greater amount of hop to your BB.
Still own my VFC never sold it. Currently has a HS SSG build in it. Might sell it though have a issue using it and not wanting to scratch it.
The stock nub is fine as long as you aren't planning to add a SCS or a Rhop patch. If you go that route pick up a systema or guarder clear bucking.