Final PWB thickness depends on your requirements. I have built 16 layer boards in .062 thick. This could not have been done several years ago. There are many ways to skin a cat, the following is one example. It is heavy impedance high I/O product. I have also done a double blind 16 layer (8 over 8) in .062 thick. Today the tuff tuff stuff are those .093+ parts with the .8mm pitch. The following was pasted from an excel sheet and I deleted some verbage; the final board met the .062+/-.007. I would be able to do a layup for you but cannot send enclosures via technet [which is a good thing]. Cheers, Boston Brad plating 0.0014 Diff Pairs = 100ohms differential 1 top 0.0006 .004 trace width B 0.0040 .004 edge to edge 2 sig 0.0006 Core 0.0030 3 GND 0.0006 Plane B 0.0040 4 sig 0.0006 56.109 ohms .004 trace Diff Pair Core 0.0030 5 sig 0.0006 56.109 ohms .004 trace B 0.0040 6 GND 0.0006 PLANE Core 0.0030 7 sig 0.0006 56.109 ohms .004 trace ) B 0.0040 8 sig 0.0006 56.109 ohms .004 trace Core 0.0030 9 GND 0.0006 PLANE B 0.0040 10 V3p3 0.0006 PLANE Core 0.0030 11 sig 0.0006 56.109 ohms .004 trace B 0.0040 12 sig 0.0006 56.109 ohms .004 trace Core 0.0030 13 GND 0.0006 PLANE B 0.0040 14 sig 0.0006 56.109 ohms .004 trace Core 0.0030 15 sig 0.0006 56.109 ohms .004 trace B 0.0040 B 0.0025 16 bottom 0.0006 78.776, 71.53 .008, .010 plating 0.0014 0.0679