Pilots all over the US and the world used these in a 4-2 run many times, I setups about 80 of them for US pilots, many for tuned pipes running a 4-2 cycle, people used anything from 12x5W Revups to 11.5 x 4.5 CF props, 11 x 4 3 blades and many other combos
By the way they made a F=front intake and a R =rear intake in these 40s,
The were made in steel sleeve alum piston ringed and ABC ring versions for the Gold Cups, and later I had made ,true ABC setups that were ringless for many the many I setup for people.
I have lots of parts, and a few whole engines for the HP40
Bill Werwage used one in his USA-1, Pilots like Bob McDonald used them in later piped airplanes
I still get them in today to setup or rebuild for pilots.
MECOA has bought the company and owns them now
Randy