Richard,
 
The most informative way to transfer information about the materials and
construction of a pcb on a drawing is to shwo a cross-section of the
construction. In this coss-section, you should indicate the dielectric
thickness requriements. Only give those thicknesses that are critical to the
design, such as overall thickness. Don't close end dimension the total
construction, thereby handicapping the fabricator.

Also, include the desired finished copper thicknesses, for each layer. It is
not up to you to specify the starting copper weight, since each fabricator
may choose a different method to give you the desired finished product. In
any event, the end result will be the same.

As far as the thicknesses specified in the IPC-RB-276, they are minimum
thickness after processing.

If you have a specific application, such as controlled impedance, then you
would have to specify a specific thickness. Or at least design to a specific
thickness. I prefer for you to give me your impedance requirement, an adjust
my construction to provide you the impedance with the tolerance that you
desire. I like this better, because everyone's materials react differently
during processing, and the fabricator is the better judge for what
adjustment factors are necessary. If your engineering has done it's job
properly and has taken into account all the variables of the manufacturing
process, then you can specify a specific dielectric thickness.

Regards,

Gary Ferrari
Chairman - IPC-D-275