My thoughts exactly. If you bet big, and are successful, you'll lose outs left and right. The book will try to get your money, but they'll also help you evade some taxes if you cooperate. They have to, for you to continue to bet. And when/if you continue winning, they won't have any leverage, they'll just have to shut you down - but at least then you should be able to stay under the radar for all those previous bets (where, hypothetically, the book manager let you get away with some things that are not 100% in line with every applicable regulation)
I'm trying to say: maybe go back there *now*, before outcome is settled, and have a good long talk to the line manager, and his manager, and their manager.
They all want your action. For now. Make it count, get them to be honest AT LEAST, and at most, make them cooperate and cover up some potential evasion. They won't be as agreeable after you go 4-0 after the first few bets.