Good job!
I remember when I did mine. The needle was on the line by the R and I still had 5 + gallons in there when I drained it.
The screen in my tank came out amazingly clean, but I had been running B20 for a few months, then a tank of B99 before I drained. I did not want that nasty D #2 smell in my yard or on my body. I was not sure how messy the job would be. It turned out to be pretty simple and clean job.
So, I just blasted the tank strainer with carb. cleaner, installed a new o-ring and put it back in there.