The Project Pad

Single throat with 66mm bore?
Or progressive with 34mm primary and 52mm secondary?
How do you calculate surface area? pi x radius squared?

So the area of the 66mm bore is: 3,419sq mm?

34mm primar:y 907sq mm
52mm secondary: 2122sq mm
total: 3029sq mm

I assumed the combination of the two smaller bores would have more area than the single 66mm bore, but the math says otherwise!

Looks like you answered your question.

I'd say the single, the double looks like its angle of approach is WAY too wide. IIRC you don't ever want more than 7 degrees on an inlet or outlet or the flow gets really turbulent.