I didn't have screws to do the side mount and I am personally fine with the back mount. I adapted this design to be mounted in the back by reusing the end piece again and shortening the length of the spool section.
I like this design and idea, unfortunately this does not work for some spools. I have this old spool of Ninjaflex which really needs the help of a bearing-mounted spool holder, but it does not rotate freely on this because this model needs to be longer to accommodate the width of the spool.
Needed something like this because I was having issues with the spool turning when I was using TPU, any kind of resistance would cause the filament to not feed in and I would have the printer printing nothing. But awesome make and thank you very much.