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Diggin got there before me. Contact your block supplier as most times they will engineer for a couple bucks a foot. 9' high, I like the Sienna stone too, cause of the long lines, but its about $25 a square foot at cost.
Our first big project was 600 ft., but not over 5' high. Had to jack hammer down in bedrock to install steps and some base. PITA. Didn't make much, but learned oodles.
At 9' high look to use larger blocks to minimize your install time and create larger lines. Small block like Pisa 2 lose their character in that quantity IMO.
And just a thought on working for an engineer/homeowner. Be ready for 1000 questions and 2000 opinions. I put in a patio for one this summer, and the guy was pretty cool, though he did just what I said. When I came back after 2 weeks to resand he said that all his neighbors loved it, but he stole some of my thunder by telling them it was his design, which it was. I asked if they were impressed that I made it work regardless LOL. We both got a chuckle out of that one.