In the mid 70's we did exactly what you are asking to a close relative of your motor, a baffled iron piston O.S. 15. And as I recall, also briefly to a OS 35 S, an even closer relative. Although neither of these engines were really designed for high power...

On the 15, we removed the venturi entirely so that there was a gaping hole in the crankcase, probably twice the area of the original venturi. To compensate for the loss of fuel draw / suction, into one of the backplate bolt threads, we screwed in a "pressure tap" - a threaded hollow nipple. This was an O.S. option at the time and even today should not be too hard to find something that fits. In case you don't know, you connect the nipple to one of the vents on the fuel tank ( and seal any others off ). The crankcase provided a source of pressurised air and ensured a steady fuel supply to the engine, even during sudden changes of direction ( we flew combat wings at beginner level ).

I seem to remember the 15 screamed ( probably in protest ) after that. Today with a little more knowledge learned, I would use a larger venturi, even if I had to make one, as the air entry is far smoother and this is likely to give even more power than leaving the venturi out altogether.

I think on the 35 we used the larger of two available venturis but it wasn't much larger. I don't recall how much effect this had, probably because the plane didn't fly very long before it was crashed.

Of course even simpler is to raise the nitro content as said above. But if you go too high, you presumably will need to fit one or two extra head shims to bring down the compression ratio.