Not too hard at all, I actually had some code in there doing exactly that at one point, but I wasn’t able to see it improving the accuracy so I turned it off
The way it was working was just to add a little extra length to the lower belts (since this is mostly an issue in vertical orientation) when the tension was really high in the upper belts…basically if there is already a lot of tension in the upper belts from geometry, we don’t need to add to it much with the lower belts.
It looks like that code has been removed in a clean up at some point, but it should be too hard to add back. The equation for calculating the tension (from gravity in the upper two belts) is here Layout-Simulator/index.html at fae9aac7993970c854167b2db4b14203ece098e9 · MaslowCNC/Layout-Simulator · GitHub