I didn't have any signs of over pressure up to 9 grain with the 200 gr. XTP. So I don't think there is a problem to go over max listed. However, I don't see any reason to either. The more powder I added the velocity never really went up. This speed of powder with the heavy 200gr. bullets is at it's limit at 1170-1180 fps out of the standard length barrel.
My experience is that I need to go to a slightly slower burning powder to get a little more velocity. Using max loads of LongShot with the 200gr XTP I still had about .090 gap between top of powder and base of bullet which tells me I can and should go with a slower powder (takes up more room). I prefer 98%-100% load density.
My next powder to try for this 200gr XTP bullet is 13-13.5 gr. of AA#9. I hear it meters well and load density should be perfect. CCI Mag primers will be used. Looking for a goal of 1200 fps.
If your happy with 1170 fps from a 200 gr. projectile, I would say LongShot is a great powder. Meters very well, burns clean with mag primers and is the only choice I would use from Hodgdon in the 10mm with heavy bullets. I hear HS7 burns dirty which is not what I want when I'm shooting 300 rounds in one day at the range with tight clearances on a KKM barrel.
Still can't wait to reload using AA#9.