RE: Picco P-zero 0.8cc
Andy, in all the years I've ran them I've never had a Cyclon or Fora broken down to see first hand how the wrist pin is held in. I assume the wrist pin is hollow and is fitted with a teflon insert that rubs the cylinder wall.
The head button that is clamped down with 4 screws obviously works well enough for G&Z to hold a fist full of 1/2A speed records but it is a source of trouble over time. The buttons need to fit very tight into the liner to postpone erosion from high frequency vibration. The speed flyers might not care because the head buttons are considered "consumables" in their minds.
Mark Rudner published a "How To" article a few years back that showed how to break down the Cyclon .15 over at the MACA website..so there might be info over there for the .049s.
MACA stands for Model Aircraft Combat Association [just in case a search for MACA comes back with 10,000 results]
Aspeed...I had guys tell me that the reed valves were the limiting factor [they would float or flutter]..but they were proven very wrong once I saw a Killer Bee turning a 4.2x4 APC at 28,000 on the ground and easily over 30,000 in the air. Figure the reed is pulsing 500 times per second.
With the lightened piston the KB will hold together at this speed pretty well. I've never shaved a Cox piston far enough down to see one fail. You can make the side walls as thin as a 3x5 index card.