The design was pretty nice, but i constantly hit the usb's and they fly from the holder

By placing neodimium magnets on the bottom slot of the USB's and also on the base you can make it be very stable.

You can even flip it upside down and they won't fall

I used neodimium magnets with 6mm in diameter and around 3mm in width, the slot it's pretty tight for the magnets, but if they keep coming out, you can glue them