Ray,
Its a bit of work, as you can imagine. Material handling is one aspect, as well as all the fastening required.
Are all your seams breaking over timbers? In some cases 3x can be laid up with staggered seams 'in the air' and not over a structural member. This requires special care in square cutting, the ends, and making sure your layout is done per the engieering specs, etc.
I have a vague notion of being able to get the material pre-drilled. You might want to check in with the mill.
My guess, easily 3x-4x the labor of putting down 2x.
