I had belts in mine and was glad I had them on a couple of occasions. I read of a guy that had a minor fender bender in a bucket and nearly went over the windshield. I liked them on curvy roads, since they kept me from sliding around in the seat. Like you, mine were attached to the body of the bucket.

Of course, the down side is the possibility of getting the car upside down and having the belts pin you in. Since it's very hard to fit an effective roll bar to bucket, without the RB being a greater danger than a wreck, it's a chance you take.