The silicone end pieces on penis pumps are bad in my experience because they cut off blood supply and make it difficult to take the cylinder off or put the cylinder on.
I don’t think most pumpers use them at all unless they’re using an extreme diameter tube, but even then many don’t use them because they have enough of a pubic fat to easily seal the tube. Pubic hair can cause a problem with the seal, which usually is a negligible thing when using an electric pump but a real problem with a hand pump. Many pumpers shave their pubes to get a good seal, but if your erect diameter is close enough to the diameter of the tube it will still seal easily with lube. Pumping does unfortunately rip out pubes a few at a time.
Like others have said, packing is when the penis expands enough girth wise to be in contact with all sides of the tube below the glans.
Starting: 7"bplx5.2" 2017 (shrunk from disuse)(originally 8"bplx4.5", gained to 9"bplx6")
Current: 9.0"bplx6.125" 2020
Goal: 11.5"bplx7" 2021.