Arnaud Dupuis held a class today showing visitors how to port Tizen over to their Nexus 7 with the latest image from himself which I have posted a link to below. The slides were shown alongside this to aid with the process. Although this is very brief it gives a jist of how to port Tizen to the Nexus 7 for somebody with a little technical knowledge. There are links at the end of this post for further research.
What is kexec :
Tizen ROM (Wifi Nexus 7) For 3G Nexus 7 just look in the directory of this file, Arnaud Dupuis posted a ROM.