And just a quick update - based on some more internet research and talking with an actual mechanic, I'm revising the 'normal operation' temperature ranges down to approx. 950F for low rpms (VTEC-e ranges), 1100F for mid-range rpms, and 1300F for high rpms (power VTEC ranges). The magic number which fits in the overlap of operating regimes for my engine with these temperatures is 25.5" (or 51" for the 'long' system). Hopefully a more accurate estimation, and helpfully shaves off a few inches
