Oh yeah, I forgot to post some progress! And no, the bolt on is so I can change fuel hole number and diameter. (Fueling is set up like most of my motors; outer distribution volume and holes in the intake flare at the CC)
I ran it the other day. Went really well, and ran right out of the box. I could tell I didn't have enough fuel jet area, as I was not able to over-fuel it.
The oddest thing happened, as I ran the throttle down to go low. It spit the intake out. It still ran, though, with a 2" long intake with no flare! The intake and exhaust are both 1" od, .035" wall. That's going from about 4.5:1 to 2:1 on the intake aspect ratio.
The frequency jumped way up after spitting out the intake, but it wasn't "howling mode". I wish I'd been doing thrust measurements and taking video at the time.
Hopefully Sunday night I'll get some video and thrust, then move on to adding the tuned pipe tail I'm planning. I want to shorten the sliding portion of the intake so I can adjust below 4.5:1 ratio as I cannot now.