Hark,
I don't use the .8 2 speed on either of my cars. I do use the LW upper deck on both. It doesn't save too much weight though. What it does do is allow the car to flex just a bit more. I also run only 2 screws in my side brace to create a bit more flex as well. Before any of you start in on me about how a stiffer chassis is always better, this subject was beaten to death waaayyy back. The setup I use right now is similar to the one Hara uses on his R40 and I really like it. It gives me a large sweet spot, so I can keep the car planted easier as the track conditions change durring the day.