Custom boards on Arduino IDE 1.6.0

I just installed arduino IDE 1.6.0. I typically don't try new things. But I did it because users of my latest devices will likely download the latest thing to try out. What I was able to do in 1.0.5 with Mighty1284P processor mod to the IDE is no longer seen on the new IDE after I pointed the arduino sketchbook folder to the correct location. I dug into the new IDE's folder. What used to be hardware/Arduino/ in IDE 1.0.x is now split between hardware/arduino/avr and sam folders, same as 1.5.x that I've never used. I wish they made a guide to modding IDE that I can follow. So other than the obvious, creating these folders in arduino sketchbook folder under hardware/arduino, what else should I do?

Thanks.

I guess this Arduino Hardware Cores migration guide from 1.0 to 1.6 might help.

Wow! Didn't expect to find something on official github. I'll do the full specification just for learning credits ;)

I just did the modification per the github wiki page. It's working! Now I just need to iron out the kinks of the new avr gcc in the 1.6.0.