I happened to have Cory's DASA (SS) 85 mm cylinder when I got my 89 mm (SS) X-Scream in. They are both works of art. Port timming are similar but shapes are a little different. The DASA cylinder is about 3 lbs. heavier. X-Scream clears more alum. around the cylinder to give more even cooling, also the smaller bore of the DASA adds material and weight. The scream cylinder has those cool rave valves which are smaller and lighter, I understand that DASA has a version now.
I bought the Scream kit because I felt that Chuck and Pat are more committed to the sport than DASA. This is all they do, if I have a question, I shoot Chuckie a PM, the next morning he sends me a responce. I don't mean to knock DASA, they are great innovators and have a great product, but I feel their focus is on four stroke bikes. You can't blame them, that's where the money is. Besides, Im an east coast boy and they are close to home.