I just thought I'd chime in with an update:
First of all, my 26.9" NXG OS @ SW2 has grown on me more. It is by far the best all-around performance racquet I've ever created. The only downside that I had mentioned before (less spin) seems to have disappeared after a day or so of adjusting to the frame. Now I have no trouble hitting dippers when I need them, and I have amazing control and precision on all types of shots. The racquet seems to retain the benefit of a flexible frame (nice spin), while giving me the pop and precision on volleys of a stiffer frame. And stability on returns is so far off the charts it makes my old SW2 setup feel like a K-mart frame. Serving, the power level is about the same (or even better) than before I shortened it, but control on serves is by far the best it's been compared to any other setup with the NXG. I'm not hitting ooh-aah Roddick-like 7-feet-up-the-back-fence power like I have with some more powerful frames (like the leaded O3 Red), but the control gives me confidence that I can hit my spot. Since I started using this setup, I have now posted 2 consecutive 6-0,6-2 thrashings in my 4.5 USTA doubles league, playing with 2 different partners. My forehand, especially on returns, is better than it's ever been, even though I'm not playing that frequently. Did I mention I love volleying with this frame?
Second: I tried shortening my other NXG down to 27.12". When I added the lead, the result felt very similar to the way the racquet feels at 27.5". Weirdly almost no difference. Now that I had gotten used to the more solid feel of the 26.9" version, I'm planning to cut this one all down to 26.9" too. This stick is 5g heavier stock in the handle, so I'm praying that I'll be able to match the weight and playability of my other NXG.
Third: With my 26.6" O3 Tour OS, I couldn't find a weight distribution that performed well on serves. I probably need to drop the tension and go back to the 12-oz., even balance setup (which I liked except for the underpowered groundies) to get enough pop on serve. The lack of leverage seems to be a problem. My sample size is small, but for me so far, 26.9" seems to be the optimum length for an OS frame.
Fourth, I cut my Warrior OS down to 27.2". It plays better than it did at 27.5", and serves slightly bigger than my NXG. But as before, it still doesn't seem to do any one thing special for me. This one may get further shortened on the chopping block.