I know the build section is here mainly for people to share their ideas to help out other people and I didn't think I had any pictures of how the chassis is designed on mine when I was building it and I still haven't found any pictures, but I am working on another one off of a jig identical to mine. Other than being 2" longer to compensate for the 6' 5" guy that will be riding it. I did find a couple pictures of it to share before the square tubing motor mounts are added in.
Notice how the engine sits down low in the chassis where the tubing is dropped down. Helps lower the center of gravity an inch lower i believe is what it is and it also make the chassis a lot more ridgid due to it being on a seperate plane from the rest of the tubing. All of the mowers must have a stock frame/rails (of course) but the frame rails are not put on yet on this mower. I do all my measurments on the frame and sit it out of the way until everything is welded to the chassis. (Makes for a lot cleaner work and not the hassel either).
This is the base chassis for all of my mowers. The only main difference in them are the lenghts to fit the driver. You can kind of see how the tubing is bent to drop the engine down inside the frame.
Here is a side view of the same mower with the transaxle mounted and the steering installed.
Here is a view from the front with some wheels and tires stuck on it. I know the camber is off they were 3/4 hubs and this guy wanted 5/8 spindles he just wanted to see it with tires and wheels on it, but it is a pretty good view of the motor mount
Note: This is not the same mower just some pictures to show how the chassis is designed.