Is it possible to modify a 2.5" cylinder into a usable 2.25" cylinder?

I can’t afford a real pump cylinder, so I use a gravel cleaner tube that’s 10 by 2.

I’m outgrowing my current cylinder (The head of my penis is huge and expands like crazy), so I’m trying to move up. Unfortunately I’ve only found 2.5” gravel tubes. I feel like the 2.5” tube might actually be better because that will allow my head to expand as much as it wants with no friction on the sides of the tube, but I’m worried I won’t be able to achieve a seal on the bottom. I’m thinking about buying the tube and using numerous coats of plasti-dip until the base is roughly 2.25” in in diameter for about a half inch up the tube. Can anyone think of any reason why this might not be a good idea? Has anyone done anything similar?

Yes you can. I myself have a 2 1/2 inch diameter tube and use a reduce from home depot that is a 2 1/2 inch to 2 inch reducer. You will have to look around at your local hardware store to see what you can find. Also, I think lapdist also makes silicone reducers that are very comfortable. Or maybe its picturebrite.

Has it caused you to get a baseball batt effect at all?

Not at all, but I did shave down the inside of the reducer a little because of the sharp edges it had which makes the 2 inch opening a little bigger.