SiRF Star III custom Firmware

I have a SiRF Star III development kit from SiRF. Included is the code to create your own firmware. I’m looking for some advice if anybody has experience with SiRF GPS firmware.

SiRF’s included documentation is lacking in many regards. They tell me what interfaces they have created to configure the GPS but not were to place the function calls. Anybody here know where to put the calls? In particular I’m looking to set the elevation mask depending on the type of satellites in a given constellation.

Thanks!