Dave Hauk and I have done 5-6 of these windshields using 1/2" plastic spacers with threaded bolts that screw into nutzerts set in the channel. The 1/2" spacers fit almost perfectly to bring the windshield flush. For those that don't know what a nutzert is, it is basically and rivet with a threaded tube that the bolt screws into. You drill holes in the channel and set the nutzerts, then drill he windshield and put the the bolt through the windshield and spacer into the zutzert. No matter what method of attachment you use, do not over tighten the bolt or screw. We have had zero problems with cracking by tightening firmly enough to get the bolt/screw snugged down flush but no more. We have had no issues with bolts backing out. We spaced our attachments about 6" apart. Also be careful with your chamfer depth.
We started out thinking we would silicon the channels but ended up either leaving them alone or using 100mph tape (sounds better than duct tape) on the outside seams. By not siliconing the seams we can take a windshield off in literally five or six minutes, and it is really convenient when you are doing work inside the car, particularly things like extensive wiring, dash modifications, etc. Of course, we don't get a whole lot of rain in AZ, so we are less concerned with water integrity, but that's a priority you can decide on for yourself.
Good luck with your project!