I've had a chance to run a few more saws on the dyno. I borrowed my neighbor's minty fresh 562 when he wasn't looking and it managed 4.4hp at 9600 and 2.6ft/lbs at 8600. My 288 went 5.8hp at 8900 and 3.8 ft/lbs at 7700- I think it could have managed a higher torque number if I had pulled it down lower. My experience so far is that it is easier to get a reading from the bigger saws, the numbers don't jump around as much. I ran 3 back to back pulls with the 288 with no issues with the dyno overheating so I think it's ok in that respect.
I spoke to Kevin at Performance Trends today about data acquisition. Looks like it's going to be over a grand, but I think it's going to be a necessity to get good repeatable results. Might have to sell a saw or two to do it, though