Tried this setup today, about 74 deg, light winds, somewhat humid.
Set my length to 29" from 27. ES pipe, AGM header, GT33, Falcon 20x10 carbon, 90 octane.
Upper RPMs dropped to 71-7200 from 75-7600, set mid throttle stick to a little over 5K, will idle reliably at 1600. Worked on throttle curve and came out fairly linear (photo). Throttle response is excellent over the entire range.
Bumped up the idle to 18-1900 as downlines were to slow. At 10lbs 11oz vertical pull was excellent. It still has the increased torque, just not the high rpms. Could pull any size radius over the top.
Only complaint was the sound wasn't as pleasing as a cannister, other than that this setup blows away any cannister setup I've tried. It actually feels like a cannister setup while flying. Downline breaking is phenomenal. Didn't miss a beat over 8 flights, that's 1.5 hours of airtime. Will have to see how it does on a hot, windy day. I'm pretty happy right now.
Excellent RM. The curve is similar to what I use.
Don't forget that a soft mounted engine drops the dBs a lot. Also, an exhaust disperser produces a mellower sound. The late Karl Mueller made these for the guys. Since they are no longer available, I came up with an alternative that works surprisingly well and is lighter. I'l take some photos and post later.
It's made from a 1" length of aluminum tube, 1/2" diameter. I used typical hand tools for mine but a mill would make small work of this device. One end is cut to produce 6 teeth of about 1/4" in length. Teeth are then bent over coming together at center. There is just enough room remaining forming slits where the teeth come together, which work well to disperse the exhaust and its note.