The cabinet under the top is supposed to be temporary until I get things going in my shop and can build something better. Unfortunately, some of my temporary fixtures in the past have become semi-permanent because of no money, time, incentive, etc.
I posted my simple top "fix" to possibly help someone else that gets an unlevel top. Forty years ago, if you had given me that top and asked me to make it flat, I wouldn't have had a clue on what to do. I started working when I was 16 and was blessed to have many jobs that taught me how to repair/McGyver many different things.
I may let Marc know what I did, but to me, the flaw isn't bad enough to send it back. If the top had required machining of some kind to fix it, I would have contacted him about a replacement.