Thanks John. Now that I know I'm a little over, I can fudge it down a bit.
Nat,
It took two chains to do those posts. The real killer is the long, deep cut you need in order to get to a flat surface.
The first blade had been on the saw a bit already, so it wan't sharp to begin with. The second blade was brand new and it lasted through everything else I did.
As for cutting without the guide, good luck. Non of my cuts are straight. Some are better then others, but that's the best I can say for my skills.
Short pieces might be easier, but keeping the blade horizontal will be as tough a job as cutting in a straight line.
I'd advise cutting it extra big so you can plane down the gouges.
I wanted gouges in my beams and was worried it would be too smooth. I was even working out ways to distress it when I finished cutting it because I expected it to be smooter. Fortunately it all worked out just like I wanted it.