I'm building one now. I have the Humm-V body on my Tmaxx, and because it is so angular and square, no stock cage will work on it.
No, it's not easy. I broke a $30 tube bender on my 4th bend. Couldn't find a rod bender at any reasonable price.
$30 bucks down the tubes, but I'm able to do the rest with a vice and hammer. It leaves dings, though.
Also got a Map gas and Oxygen set up for $50 to braze all the joints. I don't have access to a welder any more.
After that's all done, the rest is easy. Grinding the corners and painting it.
Then it's getting it mounted.
It's a good amount of work, but what I always enjoy is the challenge of building something and the reward at the end.
So, all in all, it's worth it.