I have a question... Does anyone know what the "vent mod" to the solo is?
Can you tie it down a bit more? As a guess, there were (I think) two different guys early on who carefully opened up the four vents in the floor of the bowl, at least one naming needle files for the task. Looks a little dodgy to me, but they said it was 'a great improvement' in ease of draw. I think this was before PVHES got popular but could be wrong there. Those stems, of course provide different vents in with the grooves....in addition to easing the flow with the notches.
I doubt the air contribution through those holes is significant. My attempts to plug them didn't cut production all that much (although I kept knocking the stubs of toothpicks out of the holes.....). I also think if air though those holes was a significant part of the design they would not have put the rim of the stem squarely over them?
Anyway, it never caught on near as I can tell? I'm not inclined to mess with mine, FWIW.
I hope that's the answer you were looking for?