I believe I have a 10" notch but it might be less. I know it is more than enough for the tires I'm laying out on. My bump stops are inside the notch and are about 2" long.
You definitely
don't want to cut the frame in half and try to reattach the rear section. That would be a real PITA. If you are going to use ***************** use the notch pictured below, it doesn't sound like you'll be up to making your own the first time around. Also make sure you are using a quality 220v welder.
http://www.*****************/notches/8-pc-step-notch-kit
[img]http://www.*****************/files/8-pcStepNotchKit.jpg[/img]