Dual balloon fuel system for .010s

I have this book  bought together with the Proportional Exhaust Throttle (PET) system including the balloon tank and accessories from the inventor and patent holder, the late and great Richard Freiheit. Unfortunately he passed away since then. The PET system, although a bit more finicky to set with its tiny screws, than normal exhaust throttle sleeves, works quite well. It is made of bronze, and sitting snugly on the cylinder when cold, but loosening up a bit when hot for easy throttle, due to the higher thermal expansion of bronze than steel.