Since I screwed up my response the first time, I'll tell you what I've done in your situation. In fact, I did some DC 500G G's tonight.
1. Measure the center bolt length and thread lengths you need and mark it.
2. Thread on a 6mmx1 die and cut threads down as far as you need.
3. Cheap hacksaw to cut the bolt to length.
4. File to clean up the end.
5. Back the die back off the center bolt - you're good to go.

Takes all of about 5 minutes.