FWIW...

3.75 x 7500 = mean piston speed 4688 ft/min; max 7363 ft/min
4.25 x 6500 = mean piston speed 4604 ft/min; max 7232 ft/min
4.25 x 7000 = mean piston speed 4958 ft/min; max 7788 ft/min

https://www.racepagesdigital.com/pi...ctive-forces-at-work-inside-your-engine/