I am in the planning phase of a passive solar home built in three tiers set into a hillside. The 'back' will be cement block or reinforced concrete. For the 'front' I would like to use a post and beam design, which I will work on feverishly until spring. The real question here is this...

When clearing the land I will have to remove about a dozen old growth Oak trees - mostly white and red with a few black. These trees are strait as an arrow 70' or so tall and 18 - 24" wide. I know I could cut them into lengths and use a portable mill to create great beams and posts, but I really like the look of unfinished logs for posts. Does anyone have experience using a post of this size? I have been giving it a lot of thought, and it would be no small task, but four two story trees climbing through the basement would be an amazing looking way to support two floors and a roof.

I am not asking for structural advice per se, as I will certainly consult an engineer for the nitty gritty of the design, but am I just being overly ambitious? Should I suck it up and mill all of these amazing logs into traditional square shapes?