We played this again with over 8 people on each team. A few notes:
1. Balance in the first stage seems better. I still think it'll be tough against teams with multiple sentries, but overall it went quite well.
2. There's a rock directly outside of blue's first spawn. It's possible to get stuck between it and the ground's displacement. Once you fall in, you can't get out.
3. The second stage is far too open in the first section. Also, since the spawn is so far back there's really no way to get set up in the first part so it really doesn't get much playtime. I think another building over the track after it goes up the ramp would be excellent, and perhaps include a forward spawn in it.
4. Demo of it is available here:
http://yinyarr.com/Automatic_Demos.aspx
5. Far more detail is needed on the second stage.
6. You might want to rethink red's spawn on the second stage. It's really tough pushing a cart past the spawn to win. Generally it works better if the spawn is behind the last cap. One solution would be to close off some of those passages out the front of the spawn to force people out the back. In addition, the spawn is somewhat confusing right now. Signs might help, but simplifying it a lot would do even more.
Overall, very nice changes so far.