The Aero-Vee engines seem to be working out okay, but since they weigh
at least 160lbs, they might seem a bit heavy for the thrust produced.

They supposedly make 80hp at 3400 rpm. It matters little how much HP
they make, what matters is how much thrust is applied to the aircraft.

You could have a 200hp engine on a Sonex, but trying to dump it into a
54" prop turning 3400rpm would give you very little more thrust. IOW,
the props are less and less efficient as they turn faster, get smaller,
and use pitch to load up the motor.

Another downside is that when props turn much more than 2600 rpm they
start getting noisy.

How much static thrust does a Sonex built according to plans have with
either an Aero-Vee or a Jabiru 2200? With a 72" prop turning at 2600
rpm, I would think 80 hp would make 500-600 lbs. I wonder what 80 hp
into 54" at 3400 rpm would make?