Just to clarify....Cody is REALLY ANNOYING
...but this is an "in joke" between us, not a real disagreement or anything close.......
The proper cruise for the DeH is to pull her all the way back to coarse, as it was designed as a "two pitch" airscrew. In reality it was used as a variable. You DO need to watch the "minimum RPM at maximum boost" figure if you are going flat out and pull into a climb, for instance.
Somewhere between 2250 and 2600 is the combat cruise range at 4 1/2 boost. With a little lower boost (say max weak mix 2 1/4lb) you can dial her all the way back and may get a lower RPM count...BUT don't go below about 1,800 for any length of time.
1500 is "slow flying" but it is difficult to achieve.
Climb setting...best at +6 1/4 boost and 2600. You need to adjust the control every once in a while as boost falls to maintain the 2600 though. Remember this is not a CSU but a variable...more of a "flexible fixed pitch" . (and all these are ex Boost override cutout as that is emergency and not "useful" in normal flight or for sustained periods.)
Also remember that your ground speed in still air is around your height, divided by 1000 and times 5 plus your calibrated airspeed. Calibrated airspeed is adjusted for position error...where on the aircraft the Pressure Head is (Pitot) and airflow factors etc that interfere with a real reading. A list of these adjustments is in the manual. So at 250mph indicated at 18k you are actually getting pretty close to top speed. This is actually about where the DeH shines!! Don't run at 2800 or 3000 for too long...it is outside allowable limits! I can't recall the boost achievable but full normal throttle should buy a couple of extra miles per hour. I'll have to test fly it.
Climb performance, performance at height and takeoff run were the major beneficiaries of CSU VP prop. Have another look at Scott's propellor video now you have some flying time.
The weight of the new props plus the other gear added at that time meant that top speed actually dropped....this is modelled by Accu-sim.
AND remember this is not "modelled" by tables, lookups or anything..this is modelled by Scott building the engine then making it perform to spec. It is a measure of his skills that when you take this to a given altitude and test it...it calculates and performs to the actual engine WITHOUT tampering!!
Oh, Watts / Weybridge airscrew, want to check that figure for me again (260-270mph at 18000ft) off the top of my head sounds a touch high.