You seem to be taking your time and preparing well. I am sure your flush will be successful. I had what I would call a huge stone come out on my 5th flush. I did not measure it but it was the size of the end (from the last knuckle up) of my right ring finger.
I would be interested in your feedback on the GCG if you care to post it. I had thought about using GCG at one point, but had settled on the ACV/Apple Juice in addition to dandelion (leaves and root) and water with lemon.