I had the same issue with my Circa '62 #2, so I ended up selling it instead of cutting it down. I spoke with a guy who does fitting for Titleist out of their fitting centre. The reason he gave me for not cutting the putter down is that it's already balanced and you will throw that balance off. The other bad thing about cutting it down is resale.

That being said, there are plenty of people who have cut them down so I guess it's up to you. If you decide to cut it, I'd add lead tape so you can add or remove weight depending on how it feels to you.

Just my two cents.