Out with the 340 & in with the 410 stroker!
I have read about pro porters using air dams or featuers with the thought that they helped flow within a certain lift range. I think for the most part they were working on class restriction heads tho... Where they could port, but cam size was limited. So the trick was to get that certain window of lift to move. Where in an unlimited port, normally you try to go for the fastest, smooth flow and most well rounded flow in terms of all lifts. Then use the cam duration to fill the cylinder.
I've always used volume to slow down the air when I felt I needed to. But I also do not add a lot of volume normally, especially in the bowl. I noticed in the pics you like to remove the guide and re-contour the roof into the bowl. I generally widen the side channels around the guide on the inside bend but don't do much on the long straight side. I dont remove too much from the guide boss, although I smooth and re-shape the beginning of the guide further in the port on the roof. My thought behind this approach is when you have a wet flow situation, the added volume on the roof will slow down the airstream, which is what you want, but the fuel may want to fall out of suspension right at the SSR, especially at lower rpms. The SSR I lean back lightly but I don't shorten the height much if at all. More removing the cast finish is about it. My understanding is the SSR needs to help the air turn but there's a fine line between helping it turn, going for big numbers, and making it slam into the backside of the valve or seperate the mixture. I'll be ineterested to see what Brian says.