That's not the piston he's going to use, he's got one made by this guy. Note how much lighter the piston is than a standard one - about 2/3! Which surprised me as it looks heavier. However if you watch the second video you'll see it has the trapped ring - which he described as a "reverse Dykes" (L shaped).
So that's pretty cool.
Maybe he can make pistons for vespas...
But knowing how this crowd likes to do it themselves - here is a less complicated concept to stop what he calls "cross over" and add retained piston ring to a std Vespa piston we all have.
Trick I saw on the highest reving Datsun motors As a teen - Was to use floating wrist pins (normally pressed in) with teflon "buttons" in the end to keep the pin centered. While that was for different reasons - it is a cheap and simple means to plug the through hole.
A pin pressed from under the piston once the retaining style ring was put on could retain (ring would need hole and extended "L" portion. )
In this case - our standard pistons could remove cross over, and have retained size.
How big a deal is "cross over" ?