That spreadsheet is incredible, keep it safe. Back it up everywhere, hahaha.
I can imagine how demanding it must be to sand everything by hand, but it also shows the level of dedication behind your work. But, that puzzle-like stage you described really highlights the fun part of building, it feels like the reward after all the effort.
It is! Ha, ha, ha, ha. It even accounts for some other things that need consideration when positioning things like the saddle.
The hard work is never the fun part of the build.