Beauty!
I have not seen the 251 spec, but I really like the time and temp.  I have
seen ovens that have been off by 20 degrees or more which is why I go on the
high side.  Folks really disagree with the 30 minutes. Again I think it is
way good.  As to time increase per layer the increase depends on planes.  In
measuring weights of material in baking it was more challenging extracting
moisture between and adjacent to planes.
Relative to the volatility nature of the adhesive; it is the fragile nature
of the material that requires less is best.  Thickness and location.  I only
use it on cover coats, use 1/2 ounce to limit the fill requirement and
terminate just within the rigid; keeping that area PTH free.

Thanks Steve, I am off to the IPC book store.

Sincerely,
Brad