Pi R squared H If I had the specs, I'd the math, but if you're starting with a 25CI instead of a 28CI and the difference is stroke, you're going to wind up with more than 25CI but less than 31.
Theory, quicker revs, etc. is one thing, but math is math, cubic inches is cubic inches. It simply can not be something it's not. It could work the other way too, try getting a 500cc engine in FX by saying, "Well, it's just about the same as." Nope, won't fly.
Dale