Hi @chris,
Is there a specific thread to discuss on CC2531 firmware changes?
I had several issues with the stock CC2531 ZNP-Pro-Secure firmware (mostly locking out after adding ~20 devices), some irresponsiveness that seemed related to routing discovery storms and, specially the dongle running out of memory (I had to enable TRACE debugging to see the MEM error) making it unable to send anything after some time (probably being this also part of the issues when adding more devices).
So I have compiled a custom firmware that apparently works now quite stable (~30 IKEA lights, ~5 Osram plugs, some FLS-pp led strips, several IKEA remotes…), and I am quite sure it can make life easier for people using the cc2531. No code changes to the firmware: just tweaking configuration parameters through the provided defines.
Edit: I have removed the details from here and created a dedicated post: Optimizing the cc2531 firmware for OpenHAB and the Zigbee binding. It contains an up-to-date version of the defines, and will allow for a separate discussion not to jam the general Zigbee binding discussion 
Happy to discuss / change / adjust before my IAR workbench trial license expires
Pedro