Mine is 2.5” diameter. You won’t have to worry about that for awhile…not until you’re above 6” girth (without the pump).
About the base, I didn’t glue anything on. It isn’t so uncomfortable that it stops me from pumping, but I know what you mean. It isn’t pleasurable to let it sit there, even at lower hg levels. You might have to custom make some rubber, and glue it on the bottom.