I've spent a little more time on the Rush now and today I was able to ride it on the trails at Stony for a few hours. I think the seating position I started with is almost right on, I may move the seat slightly farther back but that's about it. The seat tube moves about 3/4 of an inch to the rear with 25% sag so that is why my static measurement showed the post so much closer to the bottom bracket. It wasn't until I was almost done riding today that I realized I had no back pain, usually my back starts to bother me a little with moderate efforts after two hours. I guess that is another sign that the fit is close. I think I would lower the bar for a short race though.
On the trails it felt very fast in the tight stuff due to the shorter wheelbase than the bike I was used to riding, that's what I wanted. It may be a little slower up the hills due to the added weight but not much. I think it's deceptive how fast you are going since the ride is pretty smooth. I had to change my climbing position slightly, I need to stay over the saddle more to prevent the back wheel from spinning as opposed to the old bike where I could lean farther forward.
Tomorrow I'll ride Pontiac Lake where it is a little rougher and see how the suspension really works. I'm also going to try a new Wingnut hydration pack that a lot of people are starting to use. It sits lower on the back to avoid fatigue. I tried it around the house, the only thing I don't like so far is that it seems to require a lot of suction to get the water to come out.