Pop up pistons in the stovebolt cylinder head do really bad things to the flame travel across that weird-shaped combustion chamber. It's a lot simpler to use a shorter rod with the same flat top piston and increase the stroke length to get more cylinder displacement and compression. The H-beam rod I'm using is rated for 900+ HP, and allows me to change the 235/261 stroke from 3 15/16" to 4 5/16". With a little bit of overbore, the 261 becomes a 300. With the same rod and stroke, a 235 goes to 270. A set of those rods costs less than $400.00. What is the point in inventing ridiculously expensive "solutions" to situations that can be addressed with simple machine work?
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!