This little pump is fantastic. The instructions are inadequate, and from the looks of other reviews, it doesn't seem like everyone knows how to work the head optimally. Keep pressure on the back of the button and push the head on as far as it goes, then let go of the button and push down more until it snaps into place. If you do this, it's rock solid, doesn't need support, and doesn't leak. When you're done, push the back of the head like a button until it clicks, then it pops right off without bleeding any air out.
The amount of air this moves is excellent. I was able to reseat a half-unseated tubeless gravel tire (650bx52mm), which I've never been able to do with a minipump before. 90cc's per short stroke is more than double the air per pump of my last minipump, and the short stroke lets you pump fast and move lots of air at low pressure.