Thanks to Hispanic Slammer for posting these install pics. They were a good point of reference as my centerstand install turned out to take a little longer than I thought.
I encountered this same scenario. Try as I might, the supplied washer was simply too thick, or tolerance on the post hole sleeve was a tad off. I couldn't believe this, after trying six ways from Sunday to wedge the washer in the clearance between stand and mount. I wound up using a 4" grinder to remove about 1/16" from the post hole sleeve on the side adjacent to the washer and deburred it with a dremel tool. After that, there was enough clearance to fit the washer.
The spring wound up being a lot easier to fit than I imagined. A little finesse with a short phillips screwdriver to guide it onto the spring attachment point on the stand made it easy.
The silly cotter pin was the hardest part. The Honda instructions indicated to insert the pin from from the front of the bike to back. Darn near impossible because there's no room to position a set of needle nose pliers from the front side with the exhaust headers in the way. In hindsight, I should've just inserted the pin from back to front and called it good. After pondering about how I would get the pin in from the front, I took a long piece of thin copper wire, threaded it through the cotter pin hole from back to front, took out the soldering iron and soldered the tail end of the cotter pin to the wire. This allowed me to thread the cotter pin in reverse like needle and thread. After the pin was in, it was easy to spread the cotter pin from the accessible backside.
I am so happy to have a centerstand on the 1200 now. I've become so accustomed to having a centerstand on my other bikes, that I can't imagine doing things like maintenance and bike cleaning without one.