I finally almost have my build completed, took it out for it's maiden voyage, but I quickly ran into a problem. The seatpost would not get tight enough. It would twist, make all kinds of creaky noises and slowly slide downwards. I applied some carbon paste hoping that would be the cure, but nope. Upon further inspection I discovered the seatpost tube is not uniformly sized all the way down. Near the top where the clamp goes is perfect, but further down it appears to get larger. So when the seatpost clamp is tight, the seatpost can still rock back and forth around 2mm (estimating), pivoting where the clamp tightens.
I emailed Linda at Ican bikes and told her pretty much but I just wrote above, along with detailed pics showing the measurements of my seatpost, and she told me this:
"The seatpost you need to use sizes 30.9mm . and the clamp 34.9"