FCPX with a reasonable GPU handles RED natively as well.
Just throw the .R3D files directly into FCPX.
To make sure you get smooth playback (unless you have a RED Rocket card), change "Choose Viewer Display Options" (the little switch top right of the viewer) to "better performance".
You might need to install the RED drivers and codecs - check for an update anyway if you haven't for a while:
[
support.red.com]
For instant answers to more than one hundred common FCP questions, check out the LAFCPUG FAQ Wiki here : [www.lafcpug.org]