Here is a video of us fitting the front cockpit tube to the body. Most people don't realize how extremely difficult it is to mount an aluminum body. I try to explain it to people that mounting the body is actually much harder than taking a flat sheet of aluminum and turning it into the body in the first place.
Here I will go through the steps of fitting a body to a chassis for the first time. After the first time, it is a lot easier (but still extremely difficult) to mount the body. The first time you have to pay very close attention to the 3D nature of the body and make sure you mount it on correctly AND STRAIGHT! I have seen a LOT of exceptionally poor aluminum body mounting jobs. I have seen exquisite workmanship literally destroyed by people who thought they knew what they were doing.