OMG! I only just noticed that this forum existed!
Where have I been?
OK, so...timbers should be cut square before hitting the machine. Wayne is ok on the edges, as long as the bottom surface of the timber is flat, the machine will cut it.
All measurements are taken from the center of the timber outwards, so if we're working with a 10"x10", I would take the average measurement of the timber, eg: top end of a 20' 10x10 is actually 9 7/8 x 9 3/4, butt end is 10 1/8 x 10...I would tell the machine that the timber is 10 x 9 7/8, and it will mill it accordingly. There is always a tolerance factored in, usually about 0.4 millimeters (y'all state-side can figure that one out yourselves).
The longest timber I have cut has been 39', and was limited to that only because of lack of space in the shop. Length isn't an issue, if there's room it will cut it.
Width, however, is limited to 20" (I think) because the clamps can only go so wide, and the tools only so high.
Crucks are out of the question, but logs are not. We fashioned rounded clamps to hold the logs, and had to rotate the log by hand for each "side", but it turned out a pretty cool product - log bents.
Let me know if I haven't explained clear enough, as I'm not very good at descriptive writing.....