I have recently looked into using a Weber 55 DCOE side draft carb.
Pretty cheap at about $560. I was surprised. Not easy to lean the mixture as
it is a
very complicated carb. It will work but the idle will be pretty poor
as it must be mounted on the beginning of the p-port intake runners.
The throat spacing is too close to mount it near the P-port rotor housings.
Besides that it would be subjected to the full heat of the exhaust manifold.
Power will
be somewhat down compared to a slide throttle due to the aerodynamic
drag of the butterflies and throttle shafts. I don't know how much. If you
take out
the throttle shaft and butterflies and use a slide throttle you will
lose a lot of functionality like the accelerator pump for one example.

It should work fine unmodified at low altitudes and with a modest HP
penalty.

Ken Welter has been flying a Weber for a few years on his Coot. I think he
is tricking the float chamber by using dynamic air pressure to lower the
fuel level.
I am not sure. I don't fully understand what he is doing. Perhaps that is
possible with a needle valve.

Paul Lamar ...No rotor no motor.

Paul,
I think we can build a new top cover using the stock needle and seat, and
float. We change the input fitting to a -6 AN, and now I can mount a control
for the main jet located above the main emulsion tubes. It would involve
main jets, emulsion tubes and the air bleeds that go in the top. The rest
gets built into the top plate, in either a strictly manual version or an
altitude compensating version. The leaning system would not effect the idle
circuit, although the end user will set his idle mixture for his home
airport altitude.
This setup will closely replicate the weber you used on the dyno as far as
runner length, and the trade off being idle quality from runner distance to
the carb. I assume you had the same idle issues on the dyno?
Larry

Yes we did. Hopefully we will get more data soon from Mark Suspinski on the idle
smoothness of the EFI slide throttle version soon. I am thinking of doing away
with the auxiliary venturis in my custom design carb because if you mount
the carb near the beginning of the runners the boundary layer thickness
of the air going into the runners is minimal. Just a simple venturi
right at the opening should suffice. It makes the custom carb  much simpler.
Float or diaphragm version. I think we can make it for way less than $500.

BTW the Wright brothers had no carb. Fuel dripped from a pilot
controlled pet cock fed by gravity feed on to this open on the top hot
plate and was sucked into the engine when the intake valves opened.
Illustrates how simple a fuel system can be with a fixed pitch
prop load.