Answers:
For calculating the delta there are a few ways that it can be done, I am getting some high level notes within the next week or so that I will then be turning into a tutorial. But I will be sharing the high level notes with anyone that needs them.
As for the changing of formulas in the calculated field, unfortunately this is not something that is available yet in Gainsight. Here is a link to the suggestion of the idea! If you think this would be useful to your environment feel free to follow or me too it!
https://console.getsatisfaction.com/gainsight/conversations/modifying-formula-in-calculated-field-ad...
Canned reports to use for RYG do not currently exist in Gainsight. There are also quite a few different ways to trend line it, but depending on what you want to report a different method is needed to achieve it.
There was a lot to this question, and because of the many different ways that it can be set up and depth of this question it was determined that a conversation with you CSM and most likely the services team would be best in order to implement the best possible practice for your environment.
For any additonal questions on this please feel free to comment.
is there an update on documentation about how to calculate the delta?