Don't install a radius arm setup. Get a 3-link. Here's a video of the radius arm unloading on mine that is very much worth complaining about:
https://vimeo.com/147398931
Others will chime in with "you need stiffer shocks, you need stiffer springs, etc, etc." It's all speculation and you'll note that it will likely come from vendors of radius arm kits. 3-links perform without any shock and spring guess work, and the expense that comes along with that.