Dude you're my hero.
I didn't know R13 had a 3D capability.
I use 2008 at work and its 3D leaves a bit to be desired at times. Whose first born would I have to kidnap to talk you into giving me a copy of your .dwg when you're done?
I'm sure 2008 works better than R13, but It's tough to beat a program designed to run efficiently on 386s 33MHz with under 16megs of RAM. When you give it a 3GHz system with over 3GB of RAM, (and it is also designed to use that much memory), it runs at warp-speed (operations that when I learned the program would take overnight to complete now merely take a few seconds).
I have not made any decisions on any release of my .dwg, .dxf, .3ds or any other format yet. This is going to represent a significant amount of my personal time - a labor of love to be sure, but still a significant time investment. I will almost certainly make some of my sub-models available (the corridor model, the intermix modules, the turbo-lifts etc.).