1. I had emailed Brian about that and he said the only difference was the size of teh driver cutout.
2. Yes
3. The original plans had the double baffle.
4. I didn't make any changes to the box. I figured Brian designed it properly.
I have seen some wild looking subs based on Rythmik drivers. I just wanted a sub. nothing fancy.
I would email Brian about the availability of the prebuilt boxes. He is very helpful.