Birdy with Kojak on the front, Plus on the back - 57min for med-hard effort, so perhaps 5% faster. Swift - 58min medium effort.
Anyway, it is slightly surprising to see that there is actually very little difference between the Birdy with good tyres and the Swift. Where the Birdy feels a bit harder is on uphills - maybe that's why I think the Swift effort is medium and the Birdy med-hard.
So perhaps if I go the weight weenie way with the Birdy it will be as fast as the Swift. Right now I am toying with the idea of 20" 406mm wheels.
Interesting! I wonder what the time would be on the Birdy with a Kojak on the back as well plus a few other parts upgrades? Schhwalbe North America shows the Kojak as being a much faster tire.
I'm not sure why you want to go with 406 wheels. Is is to get a lower cadence at top speed? It sounds like a lot of work, Don't you need to add special fittings on the drop outs?
David