If I read that correctly you certainly do have the cart before the horse.
There are any number of good reasons to rough cut stock to length and width
and not a single one for working with a 9' board if you don't have to.
Outside of the obvious ones you are now experiencing you will also reduce
the amount of warp you have to deal with by at least cutting stock to rough
length. Example, say a 9' board bows 1/4" from the middle to either end. If
you cut the board into shorter pieces the bow from the middle of the shorter
pieces to either end is greatly reduced. Not only is it, from a handling
stand point, easier to deal with, but you then have to remove less stock to
correct the situation.
When you get your stock home one of the first things you should be doing is
laying it all out, arranging it for best appearance and marking it up for
rough Slightly oversized, cutting, cutting it, then milling it to size. For
that first step I like to use a piece of chalk then as they get milled I
mark them as to which piece is going where. Usually with something a bit
more durable then chalk.
No matter what you do some percentage of stock is going to be waste, but if
you follow the above procedure, at least in principal, you will, in the long
run, waste far less stock. You'll also find milling the stock a lot less of
a painful operation. You will also have a better developed mental picture of
the finished product and what is going where in the construction.
Click to see the full signature.