Hey Matt
Gave the es pipe a try. Made up some of your couplers. You should of patented these! A lot lighter setup then teflon and clamps. Make good protection for the plug cap wire also.
The AGM header fits perfect. 20x10 Falcon carbon prop. Turned 75-7600 on the ground at about 27". Kind of hard to measure the header for length, I used the centerline.
I found it kind of peaky in the air, seemed to jump onto the pipe before reaching half throttle. More power than could possibly want. Actually found it hard to control for the style I want to fly.
I'm gonna lengthen it a couple inches and see what it does.
The GT33 has the lowest jump of the engines I've played with...... It takes considerable throttle expo curve to tame the Walbro's mid range. But it can be done and I'm doing it. Interestingly, I don't find the ESC pipes peaky at all. Just great power (and torque galore for the beefy props)
I don't know anything about the AGM engine tho. The rpm is about right on premium gas and I agree it's way more than we need for a 10 1/2 lb airplane. I have my GT33's set-up to operate at about 6-6.5K at mid stick. I fly all vertical stuff there at a very comfortable pace. It's a very quiet set-up.
Thanks on the couplers. Got sick and tired of playing with standard silicone with iffy performance. The coupler ablates the inner layer of silicone and exposes the ceramic cloth which is unaffected by heat. Works great on the YS 4 stroke too