My RV-9A was originally registered as an "Ultralight" in Australia, with a 600Kg (1320Lb) regulatory MTOW, and I was religious about sticking to it until I re-registered it VH- to get the higher MTOW a couple years ago.
With the OX-340, it would fail LSA rules on cruise speed, even without any gear fairings, she'd get along at around 125KTAS, with maximum speed being around 150KTAS, IIRC. Yes, you
could have the prop pitched to give you 3,000FPM+ rate of climb to trade cruise speed, but, realistically, it is
not a 2 "adult" seater.
I could get Me + just-under-full tanks, Me + Mini-Me + half tanks, or Me + the KRviatrix and enough fuel to taxi to the bowser to refuel to taxi back to the hangar...
That suited my mission until it didn't, and the rego was swapped over.
FWIW, my original BEW was
445Kg or
981.5Lbs for those who haven't embraced SI units yet....