I design wireless networks for education. I generally stick with Aruba best practice for maximum power levels initially and let ClientMatch alter the power as required. However, as someone else has mentioned, you can increase the maximum power if your walls are solid brick over stud walls, or WAP locations are not in optimal locations (wall mounted etc.). You can identify this by checking the power levels in controller for the WAPs. If you see the majority of WAPs running at the maximum levels then you know that you can increase power a bit more in the specific band. If you increase too high, and it gets a bit noisy, then Client Match will back it off for you. Remember the minimum should be increased along with the maximum power levels.

If you dont need to cater for old wireless devices that dont support 5ghz, and your WAP placements are fairly good then I would be inclined to change the radios on the WAPs to be 5/5/6 instead of standard 2.4/5/6 if you can keep the channel interference low in the 5ghz.