Manifold Vacuum Advance what am I not getting?

I am waiting for Ray to send me one of his Distributors. I spoke to him yesterday. When you refer to 20° you mean max vacuum right? I asked for a variable can of course so I can adjust it.
I’m trying to get compression numbers but it’s been 120°F in my shop. And I’m still not feeling up to doing it right now but hopefully soon. then I’ll post them.
You didn’t say anything about manifold versus ported though, and I’m curious to know what you think about using Manifold for my set up.
Sorry, I just read the last part of your post. You did say try manifold first then ported.