The GH file you sent is extremely slow and several attempts to run it resulted in Rhino crashing. However the Rhino file ringed a bell. Hasn’t this problem already been solved here ?
I started over from the file in the post above and simplified it a bit more.
Unfortunatelly some of the rules of this have changed in the meantime.
Because instead of the lowest vertex of the plot, we now should consider the lowest vertex of the access to the plot. And for some reason I couldnt make the previous solution work.
I’ve tweaked the file that you just sent , and this way seems to get the results that I want.
I’ll cross check on the excell file now.
I’ll leave it here in case you want to have a look.