Back in 2008 https://donkey32.proboards.com/thread/40
, I tried to mimic the so-called dry slots in one of my early rocket(ish) experiments. The slots in several sizes left and right, larger and smaller, higher and lower in a multitude of combinations or completely closed.
To the naked eye, compared to no open slots at all, there wasn't much of a difference. The Testo gas analyser could find some though, chimney temperature consequently did rise somewhat quicker with the slots open. And the carbon monoxide content in the exhaust gasses rose to alarming levels, which is a sure sign of incomplete combustion.
Without a gas analyser one could conclude combustion was more complete because of the higher exhaust temperature but in reality it wasn't, rather the opposite. The ballast gases weren't separated from the combustibles (CO being one of the latter) and some amount of the hot gasses produced went straight through the chimney into the great outdoors.
My conclusion at the time: the theory is probably flawed in the sense that the predicted effect was neither repeatable or provable.
The hallmarks of a good experiment are that it is provable, transferable and repeatable. Given the absence of two of these necessarily parameters, it's unlikely it would work according to the theory.
Just my two cents.