Hello all,
After making a new feed bottle for my reo I decided to try something. Looked at the small flimsy silicone insulator from one of my 510 connectors and kind of duplicated the profile in a way from a piece of 1/16"ID 3/16"OD PharMed tubing. I like using the stuff because it's one more thing that won't leach chemicals or break down very easily, all the better in a connector on a bottom feeder. Now if I could only get a SS connector made...
Clamped down my dremel to my work bench to keep it stationary and using a thin straight-ish cone sander piece I cut away the profile pictured below while slowly turning the piece of tubing. Makes it easier to sand it out of a bigger piece and cut it later. The inner diameter of this tubing is a little thin to slide over the center post easily so I also sanded the inside a little bit. Also makes it easier if you could slide the tubing over something solid so it's not flailing around while trying to make these small cuts.
Tested it out by screwing a carto all the way down with it and nothing on the center post seems close enough to ever short. This material is a tough rubbery type that's hard to cut even with a sharp blade yet can compress enough without causing too much stress on threads if over tightened. Makes a liquid tight seal as well.
PharMed® Tubing | U.S. Plastic Corp.
Hope this is helpful in your modding endeavors
Am curious to see better/easier alternatives y'all have come up with too, this one being tedious as it is 
After making a new feed bottle for my reo I decided to try something. Looked at the small flimsy silicone insulator from one of my 510 connectors and kind of duplicated the profile in a way from a piece of 1/16"ID 3/16"OD PharMed tubing. I like using the stuff because it's one more thing that won't leach chemicals or break down very easily, all the better in a connector on a bottom feeder. Now if I could only get a SS connector made...
Clamped down my dremel to my work bench to keep it stationary and using a thin straight-ish cone sander piece I cut away the profile pictured below while slowly turning the piece of tubing. Makes it easier to sand it out of a bigger piece and cut it later. The inner diameter of this tubing is a little thin to slide over the center post easily so I also sanded the inside a little bit. Also makes it easier if you could slide the tubing over something solid so it's not flailing around while trying to make these small cuts.

Tested it out by screwing a carto all the way down with it and nothing on the center post seems close enough to ever short. This material is a tough rubbery type that's hard to cut even with a sharp blade yet can compress enough without causing too much stress on threads if over tightened. Makes a liquid tight seal as well.
PharMed® Tubing
Can be autoclaved repeatedly. Heat weldable for sterile access in closed systems. Documented biocompatibility to ISO 10993 Standard. Meets USP Class VI, FDA and NSF criteria. Less permeable to gases and vapors than silicone. Ideal for cell culture, fermentation, synthesis, separation, purification and process monitoring and control. Independent tests show its safe for use in sensitive cell culture applications. Very good general chemical resistance and excellent acid, alkali and oxidation resistance. Opaque to visible and UV light, it helps protect sensitive fluids. Continuous service -60°F to 275°F
PharMed® Tubing | U.S. Plastic Corp.
Hope this is helpful in your modding endeavors
