For years I have used ML Campbell vinyl sealer and their nitro lacquer, with good results. My Edmonton, Alberta, Canada industrial supplier has switched to their own brand name and told me it was comparable. I used it on two new guitars I built. These guitars received my usually application scheme and were left for 6 weeks to cure before rub out. Last week necks were attached, bridges installed and the guitars were completed. Two days later I noticed severe finish cracks radiating on the lower bout, specifically spider web cracks going in all directions from the rear of the bridge back. It appears that the finish can not take the flex and vibration. Finish is always a pain, so I want to use the best materials available. From your experiences who makes the best vinyl sealer-nitro combination of products.