Honestly I think CV have lot of shots in their guns...
If you know how to modify and fine tuning the power is so close to a flatslide that the last doesn't worth the money they cost...
I'm a specialist in CV modifications. I modify also the emulsion tube closing some holes with epoxy metal bi-component glue.
During 80ies on emulsion tube there were 12 holes small. After 1995 they became 16 larger. With so much holes they obtained a lean emulsion with lot of air that you are obliged to compensate with thin or high raised needle.
It's normal to rise the needle of 4 or 6 shims (3mm, 0.5mm each shim) now, it was not normal when there were 12 small holes on the emulsion tube. So I close from 6 to 10 when I fine tune my carbs.
Also the small air passage on bottom of the Venturi became larger. Some dynojet for some bikes provide emulsion tube with small and few holes or a brass cap with a small hole to put in front of the stock...
Also the spring can be cut to obtain an anticipated raising. It works like a preloaded spring of the shocks, if you reduce preload the slider/needle will raise before.
And fuel level is important too...
