I'd be curious to learn your formula for puncturing your can lids. I used homade metal pail feeders back in the late 70's when I kept bees for about 6 years and never had a problem with them. Now I am stymied; all of my experiments with making a pail feeder this season (all plastic) failed, never achieved a proper vacuum. They dripped too much or not at all creating too much vacuum. So...I ended up buying one which works fine.