You can see in the first pic I just got the glass down and left it at that.
To trim I routed the edges of the pads after careful measuring. I only cut down close to the bottom where the release tape was. Then it was a matter of finishing the trimming with hand tools. Files and a chisel, going very carefully.
This took all day and the whole step would not have been required if I could have cut the glass exactly to size as I layed it up. Either way, job done. It looks a little rough in the pics as I still have peel ply on the top of the pads ready for the next step.