The single can holder is self explanatory. I recommend a 10% infill to reduce filament cost. 

The double is a little snug without removing the middle wall for support if there is just one can in it. The nice part is you only have to press the cans in very lightly and they will stay in place. Simply roll them forwards to remove!

I print with supports on but as there is no magnet holes in the bottom it prints okay without.