Wow. For me, a contender for the best Listener since I have been doing them. There are clearly three classes of solver - calculator alone, spreadsheet, and programmer (Java/Python etc). I am in class two, for this one, and I bow to anyone in class one. With a spreadsheet, there was a clear (with hindsight!) route. I found various steps to be amenable to logic and a calculator, but would love to hear if there is a route that I missed to solve in a reasonable time without a spreadsheet.
Radix, thank you very much indeed. A wonderful puzzle.