Please accept that the 'boost port' was never part of the original Schnuerle port arrangement but a later thought about using a late timed port to scavenge the parts of the combustion chamber missed by the twin loops of the main side ports.

And it was done for outright power.

The problem with some engines is that they are designed for a wetter methanol mix and high power outputs at high rpm's - so the pressures in the ports remain usefully high for that type of use.

Enter the model diesel that uses a much drier air fuel mix, runs happily at a lower rpm and is not really seeking great horsepower and the suffers cavernous ports with conversion engines.
You can well see that blocking off a third transfer port will direct the pressure stream to the remaining two ports, increase the pressure in those ports and lower the volume of the lower crankcase thereby increasing its pumping capability.

To do this you must remove the liner from your engine and fashion up a plug from softwood that fits nicely into the boost port's casting cavity, it will not come loose because of the curved recess that it sits into and should not burn either.
Oh, and it is only temporary and completely reversible if you do not like it.

For a more instructive lesson on this please refer to -

http://www.tulsacl.com/Engines.html

The idea on how to do this is illustrated well even though its aim is different.

Cheers.