Gradebook

I am currently working on upgrading version 1.8.9 to 1.9.5 for my school system. In 1.8.9 hidden grades were not calculated into the course total and I want that to be the case in 1.9.5.

I am aware of the work-arounds (like giving categories a weight of zero) but I am trying to code the change myself to alleviate stress from teachers in our system. I know it has been stated that it wouldn't be an easy feat considering the 9.5 gradebook changes, but I'm wondering if anyone a little more experienced with 1.9.5's code could help me with any details about where aggregation actually occurs so that I can give it a shot?

Thanks!
Erin Arnett