Try heating the end and then pushing it against a piece of glass (try some scrap first
![Big Smile [:D]](/FSM/CS/emoticons/icon_smile_big.gif)
) . Make the "Blob" a little larger than you need and then sand it down. If you want a square shoulder, put a small washer over the styrene, put a piece of fish tank hose over the other end to use as a stop for the washer. That should make a square shoulder, although I've never actually tried it.
Either that or let me know the dimensions you need and I'll see if I can cut you some on my lathe. It's just a little one, but it cuts aluminum just fine.