This is going to be a quick one: As you might have noticed, I took care of the Quimby relaunch today as Lena, sadly, will be out of office for several weeks.
This also means that for now, all support duties fall into my hands again. As usual, you don’t know what you got 'till it’s gone…without Lena, I’ve got several hours less to spend on development every day, even though I triage support requests rather aggressively and only respond to the more urgent stuff within a somewhat strict daily time box. I mean…it’s obvious that we have a dedicated team member for this sort of stuff for a reason. But not having said team member for a while really drives home the why 
Anyway, besides the above and some personal matters, I made some progress in my aircraft performance adventure:
The light red lines are the “old”, super simplified model which yields okay’ish results in some cases, but pretty bad ones in most others. The dark red lines are the work-in-progress version of the new formulas. They are way off at the moment, but they use a much more complex approach based on actual “mission phases”, with some of these phases not being modelled correctly yet:
As such, the results look very promising. The idea is to not read values from the charts but instead model the performance of a type using its actual properties (aerodynamics, thrust etc.) and then use the charts and their mission assumptions for verification.
To that end, I got me that (truly massive) book that @TWAAir recommended a couple of weeks ago from the university library, but haven’t had much time to check it out yet. So thanks for the tip 
You should be able to do most of the performance analysis in the book in Excel, which the book actually shows you how to do it