We have a 2011 GMC crew cab with a standard box with a Reese 16K slider hitch. In three yrs I never had a need to use the slider. Also, we have Montana with a Mor-Ryde
King pin. I found that if I moved the slider back with the tailgate up the back of the kingpin will hit the top of the tailgate.
We had a 2008 GMC with the same Reese slider. We just bought the Montana and when backing the Montana into its new home I slid the slider back and it hit the top of the tailgate, so i haven't used the slider since; nor did I need it. I plan on buying a B&W Patriot because the Reese hitch has a lot of chucking. I believe I read somewhere that
Reese stated their slider will not work with GM trucks.