I have a Polaris lock and ride rear box on my 2013 XP LE and in the market to get a backrest for it. I see that there are 2 Polaris backrest. One attaches to the box and the other is adjustable. Can the adjustable backrest be used with the box at the same time? I`m getting conflicting info. And which backrest is better and why. Neither are cheap but I saw them at the dealership and they seem pretty nice. I appreciate and info.