"Winging it" and "on the cheap". It's like your writing my obituary! 🤣

I like to make things out of what I can find which I have found does sometimes lead to doing things twice or 'learning from your mistakes'

The shorter drive belt on the robot is stationary, going around the moving driven pulley so I think that would be worth trying.

The long belt was on the full 6m of ali. I'm struggling to remember if that was stationary or moving. I think probably moving as the motor was on the end of the rail not the moving carriage. I think if I alter it to be stationary I could put one either side. If your doing this can you put a motor each side and run them as a pair or is it better to physically link them with a shaft?

Your eight, I need to do some planning, I will look at the links and play on cad