That was a rant sorry!
I was influenced a lot by two articles in particular, and a couple of images when I decided to do something for the SRs BS34 carb. I'll dig them up and attach them next.
In the meantime, here are a few (some stupid) prototypes I made before coming to a final design that I will have machined up in aluminum for dyno testing. For packaging reasons, this is only intended to improve the flow of air into the carb (perhaps up to 5% more), rather than try for any harmonic tuning. One of the prototypes in the picture would get the 2nd harmonic in the 6,900 - 8,000 rpm range, the third in the 5,200 - 5,900 rpm range and the 4th in the 4,000 - 4,500 rpm range. But look at it! It would be ridiculous haha.
I used some ideas from A-class automotive surfacing and curvature to achieve the smoothest entrance possible within a reasonable size - see screenshots from the solidworks files using various surface analysis tools - curvature combs, curvature display and zebra stripes. The idea is that the bellmouth bolts onto the carb with two M4 set screws behind two flanges on the carb. There is also a large flat surface on the outside of the part just past the radius to be able to squeeze a clamp-on air filter over the top of it and clamp it tight. I personally would never run an open carb/velocity stack on the street, or metal mesh for that matter. This will be clearer when I get the proper proto.