I probably should've explained it better.Trim the opening, I've only mounted a couple bodies, but both needed trimming to clear the tires
This is pretty much what I did, except I went with 2x4 boards just for a little more insurance against dragging. The tracks around me have a tendency to get very rough, so I don't want to split it first night out. I bought the JKB xact fit and it was really easy to get mounted. Be aware though, the "foot box" is very tight around the pedals.quit trying to mount the body on the kart while its on the stand and the tires on.
set it on the ground, after you have slide the body under it put 1 inch pieces of wood under the nose to help hold the doghouse up
I have never mounted a new body that just perfectly fit. I am sure part of it is on me and part of it could be using different brands of bodies but it has never been easy. As a result I have pretty much given up and went the easy route.