I don't think Cisco APs can do client load balancing. The only way you can make sure that users would not be overcrowded in one AP is to set the maximum number of clients on the APs so that wireless clients would be forced to connect to another AP if one AP has reached its maximum number.
This is the functionality which is missing in H-REAP: Client and Network Load Balancing
"Radio Resource Management (RRM) load-balances new clients across grouped lightweight access points reporting to each controller. This function is particularly important when many clients converge in one spot (such as a conference room or auditorium) because RRM can automatically force some subscribers to associate with nearby access points, allowing higher throughput for all clients. The controller provides a centralized view of client loads on all access points. This information can be used to influence where new clients attach to the network or to direct existing clients to new access points to improve wireless LAN performance. The result is an even distribution of capacity across an entire wireless network.
Note: Client load balancing works only for a single controller. It is not operate in a multi-controller environment."
I suppose if we limit the number of users that can associate with a particular AP then we will achieve some client load-balancing. Though a hard limit on the number of end-users will also lead to situations where some end users will not be allowed any access.
Thanks for posting back with your results! 5 points for your continued good work here :) Just curious if you looked into REAP vs H-REAP? I'm not sure of your other restrictions but there is some funtionality in REAP that is not in H-REAP. Anyways.......