I don't use the cage with any body. This is my Mugen body, the cage doesn't fit but the body is reinforced.
If you put in a center brace you can just put a foam block between it and the roof of the body. I did that with my Slash for a while on the Baja Bug body....Now....I just cave it in...then punch it out. It takes it. It doesn't cave in very often.
Your roller is more than likely a V1 Kraton....not a V2. It may have the old front bearing blocks that didn't do so well. You may want to change them out to V2 with Avid bearings. If you don't use a chassis brace/bar....you have to make the body mount holes a little elongated to allow the chassis to flex....if you don't, it rips up the body pretty fast from jumping and flexing.
By the looks of the pictures on that link....that's a V1 Kraton. I didn't see any detailed description saying it was a V2. Sometimes people sell stuff with older pictures but they have newer versions ? I had to contact my seller to confirm I was getting a V2. The pictures are saying V1 to me. It's still going to be cool. Look into the front bearing issue on the V1 just incase. You could just change out a few minor parts to avoid the issue. Then it's all good and updated.
Here is a link to a V2 on E-bay. Look at the red 17mm drive hubs and the size of the bearing blocks in the front. They are different. And these are different sellers on E-bay.