Yes! And it’s always fun talking shop with someone so familiar with hobby level CNC equipment
Let’s see if I can remember back that far… That early design had the x-axis belt connected to one side of the gantry, then the belt was run on top of the tracks, around the GT2 pulley on the motor, through the extrusions, around an idler pulley at the other end of the tracks, and then back along the top of the tracks to connect to the other end of the gantry. The main problem was feeding the belt through the extrusions. It was very difficult to feed through even a single 1.5m extrusion, and it would be near impossible to feed through multiple extrusions already assembled end-to-end.
The design of course could be modified to not have the belt run through the extrusion. For example it could be run underneath the tracks. But then it would probably sag onto the raised bed or dirt unless it was supported some other way. Different extrusions with a larger internal cavity could be used to make feeding easier, but no matter what you’re gonna have a really hard time feeding 6m of belt for a Genesis XL bot.
Another consideration was safety. I didn’t want large lengths of belt exposed and moving whenever the gantry was moving. It could easily catch on vegetation, clothing, fingers, etc if exposed.
Shortly after that early prototype, I helped assemble a CNC router that had a metal chain fixed at both ends and snaked around the drive gear on the gantry. I thought that system was so much better for the longer length of the axis than a full loop of belt/chain that is more common on small machines like 3D printers and laser cutters. So that’s when I changed and I kind of never looked back
We did in the early days. However, there was licensing conflicts with GRBL, although I think that project has since changed to a compatible more permissive license. And Marlin at the time did not support Rotary Encoders, and after toying with Marlin for a bit, it was determined by our firmware developer it would be easier to build something more or less from scratch than to try to integrate encoder tracking into a fork of Marlin. If we were starting over today, we would possibly (probably?) use one of those firmwares.