I milled mine similar, but I did it big enough so that I could move the battery forward and rear to use as a tuning option. Unfortunately, I removed the side guard screw holes making them unusable. I didn't like the result and replaced the side guards, so that I could go back to inline and use the side mounting screw holes. Removing the side guard screw holes and removing that much of the chassis caused it to flex too much and lessening steering.
I've gone back to the inline method. It works for me and I like the amount of steering that I have. I'm sure if I left the side guard holes in place the sideways option would be viable.