Regarding the chamber size, I have no idea how the size compares to the RS-1. I've only used the RS-1 a few times at meets, and didn't take any measurements. I've just found that I seem to like these headphones the more open I'm able to make them, so the deeper cups, open screens and lack of buttons have all made audible improvements to my ears. These cups in particular have a lot of wood beyond the chamber, for no other reason than I was a big fan of the grain in the piece of zebrawood I had found, so I wanted to keep as much material as possible after turning them. I love the face on the grain, and the depth from the face to the grill shows a lot of grain as well.
edit: I almost forgot... It's still using the stock cable. I have gone back and forth with what I want to recable it with... Stick with copper, go with silver-plated copper or go to silver. I'll decide sooner or later!