I improved the fit. They could be pulled right off with the previous file. I also added a base for it to stand on. you could also slice the base off for a more compact unit. They do lock on and stay on. you can fit 4, I only have 2 at the moment. Where the tower meets the base is quite weak, I would increase the fill or just be careful when removing the print. nothing can be done about this due to the clearance needed.
NO SUPPORTS NEEDED!!! I chamfered the only over hang so that you don't need supports. ENJOY!