For your stated goal, of gas recirculation, it's fine. Except you don't need or want the PCV valve as depicted (More about this later). However, the plenum box is a drain for raw fuel pooling in the air chamber.
This happens when insects build nests in the carb overflow drain tubes, and the float valve sticks open, and the gas selector valve is faulty or left on.
So, you have to ask yourself where that rising puddle of gas will go if the tube routes up to the engine or rises to fill the filter box.
Then if you don't notice, an attempted engine start either puts incompressible liquid in the engine cylinders, or a spark lights off the pooled gas collected. Or the filter element plugs with gas soaked in it.
The picture posted is of the Cb400 system. I don't recall if the filter box on the 350 has a separate drain hose at the bottom of it.
To regain the drain function, you might be able to adapt a PCV valve to a T fitting at the low point of the tube interconnecting the plenum chamber to the engine fitting. The valve would be open without engine/plenum vacuum (allowing pooled gasoline to escape). It would then close when the engine is running, and provide recirculation. You would have to select a valve that would close at the vacuum levels that exist in the air plenum which is pretty low and variable (with both engine speed and pressure drop across the air filter membrane). (I have never measured what the typical air plenum pressures are however, or which PCV valve designs or parameters would provide proper function for this alteration.)
Cheers,
