We've tweaked the flow gauge parameter and corrected a static error, so now that I have accurate fuel flow and TAS within 1 knot at 140 kt, I can report some accurate numbers. I chose the 81" over the 79" to get good cruise performace with one P-mag, and it worked out very well. Australia doesn't have any high-altitude airports so reduced climb is ok.
Engine: Superior XP-IO-320-A1AC2
Ignition: 1 P-mag and 1 Slick mag
Prop: Sensenich 70CM7S9-0 (81)
Static RPM is about 2240. It will climb at 1700 fpm solo with full fuel.
Top speed at 8,500 ft (9,700 DA) leaned to 75 ROP is 172 kt TAS at 10gph. It hit 2640 rpm so I pulled it back after finding top speed.
LOP cruise 159 kt TAS at 7.1 gph WOT 2470 rpm.
LOP cruise at 9,400 (11,500 DA) returning from the solar eclipse was 150 kt TAS at 6.2 gph WOT 2350 rpm. I think the lean-mode EGTs in the photo aren't accurate but there was room to richen a bit.
It seems to have gained 3 - 5 kt since I removed the tiedown rings. I didn't realize they made that much drag.
I remember reading ages ago that the Superior XP engines have smoother intake ports which results in a couple of extra hp. YMMV.