Just had a successful run where I got my first trade port up by 6 minutes and had 3 by 8 minutes.
Well, at least now I know that it's doable, even with the colony-cap rush strategy. The bad news is that it's only viable that early if there's only like 1 planet for your cap to colonize (and has to waste its time plodding towards the enemy in the star's gravity well, or in a long gas giant).
I also didn't have to research any planet colonization until the 7 minute mark or so, which helped a lot.