Hey Foosh,
The little stopper ball slidy thing is used to prevent the bar from going to full depower out of arms reach. If you are comfortable and confident in your riding ability to do without full depower and maybe use 70%, then the stopper is a great piece of gear.
I would remove the neoprene cover and then toss the cylindrical, lower section in the bag and keep it there. The stopper works fine without it and allows you to be able to push the bar away, past the stopper in times of need, and will also slip and depower in massive loads ie huge gusts and kite loops etc. This is how we set up all of our stoppers and they work great like that.
Just make sure when you put the stopper on, that the bevelled or pointed end of the stopper points downwards, towards the bar and not the kite, otherwise it wont work properly.
If you are up in the northern part of Perth, drop in to see us on the beach and we'll give you a hand, it only takes a few minutes tops.
Good winds,