SNIP

That is actually kind of my plan for my workbench, I have a friend who run a saw
mill, it does macrocarpa slab only.
I was thinking about using macrocarpa for the legs and the top. since i want a
10 cm top and 10x10 cm legs (10cm = 4"), i'm thinking about buying a 10cm thick
slab, 2m long (6.6 ft) and maybe 80 cm wide (2.6 ft). Choose a slab that has the
pith (or close too), rip it into double legs and half tops and discard the pith.
Don't know yet how much this will cost.

The only thing that is unknown to me is the stability of the wood, as he's
doesn't kiln dry the wood.

END SNIP

Yes, that is what I do with my lumber.  Typically on the near-pith strips of
oak, I have wonderful quarter sawn figure.  However, it is divided by a strip of
pith.  So, in a board that is 32" wide, after cutting out 4-6 inches of pith,
and another 2 of sapwood I will wind up with two beautiful boards,  each 12" -
13" wide.  Of course, there are always a handful that are not close to the pith,
but somewhat narrower because of the semi-cylindrical shape of the log.  From
those I can get clear, figured boards that are exceptionally wide -- but very
few.

FWIW, kiln drying is not recommended for Macrocarpa until after it has already
dried to fiber saturation.

As to stability, with green wood, you are simply going to have quite a bit of
shrinkage.  Here is a useful on-line tool to figure it:

http://www.woodbin.com/calcs/shrinkulator/

To use this you need to know initial moisture, and the range of humidity I the
place you will keep the bench.  Get the moisture through a meter, or back into
it by figuring that  green Macrocarpa  heartwood averages 65% MC, and the
sapwood is 145% on average.  You can get any of a number of tables that tell you
what the MC will be in a give RH environment, so you could calculate the
shrinkage that way.  However, the fact is that building that green will cause
not only shrinkage but warpage.

SO

If instead of green cut wood you get wood that has been properly stacked and
stickered for at least  year per inch of thickness, you can assume that the MC
will likely be between 15% and 18%.  Use that as a starting point, and refer to
the RH/MC tables and the Shrinkulator.

It seems a pain, but I do it any time designing furniture to go into various RH
environments.  Better to plan than to see all that hard work scrapped by cracks
and warps.

Cheers!

Joe