Page 152 of "Six skills and other discussions," by Steve Lewis, has a plan for 200 feet, using the 18/45 trimix. I found on my radar this after reading divingleo’s dive plan, above. Now, I have a starting point. I will not make it to 165 m, not in my lifetime. If I was only a bit younger, say 20 years younger. Interestingly, the book, "Deeper Into Diving," by John Lippmann, 1992, displays Navy tables, with deco using air. Trimix must have started later?