That's looking really good. You probably were not going to do this, but don't throw any of that cut Homosote away. You never know when you might want to add trackside scenery at a later date.
I'm sure glad I saved all the wood I cut out of mine. It has come in handy on several occasions. It sure eliminates a lot of measuring and trying to match the existing cut.
I wish I knew what I wanted to do for scenery when I started my layout; I might have left a lot of the plywood intact instead of just cutting the plywood for track only.
With the size of your layout, you might want to number each piece and the corresponding area it came from. Probably save a lot of searching down the line.