Okay, I drilled them out today. As others have said, there is a noticable improvement in throttle response. I only test rode for a few minutes, and then I had to do other stuff - so I'm hoping to get in a better test ride later. In a few days I'll have the HD spring to try out too.
For anybody who is wondering how to do this, I wrote up some quick instructions with pictures:
http://frontiernet.net/~dmclec/slide.html
