I have one of these (uni syn) and I didn’t like it much at all. But they look cute.
The hose, just put one end in your ear and the other in the throat (of the carburetors!) so you can listen to the hiss of the airstream. Then compare. I was sceptical but the uni syn didn’t make it scientific.
The pistons don’t have to be lifted much (too much and the engine will always die). I reckon that 1-3 mm should do it, just lift them a little.
This reduces the vacuum, less fuel is sucked out of the jet, and the mixture gets leaner: if the engine dies immediately, you need to lower the jet on that carburetor, that means screwing the mixture screw down. Then just check, repeat, etc. until you have it dialled in. And if you can’t get it right… start again… and again. It’ll run sweet eventually!