Well, here it is in writing from Armstrong/Bruce/ Robbins/Hartco. We have been suggesting that solid planks be glued as well as blind nailed but there wasn't a definitive example from the manufacturers suggesting this that I was aware of. If one purchased a custom floor from a certain manufacturer, they provided instructions that suggested gluing as well as nailing their wide plank floors. But those instructions only came with a purchased floor. Those New England yanks don't want anyone to get anything for free, including information. So that just left unverified speculation about using adhesives to install solid planks. But finally, here it is from Armstrong themselves, copied from their solid installation instructions on their website.

Gluing does appear to be a good idea, but what about the vapor barrier problem mentioned. Gluing on a vapor barrier isn't possible?

In this case, the installer does not use the standard felt paper. It doesn't do that much in terms of moisture protection from below. Much less then many think. The flooring still needs to be installed over a dry subfloor over a dry crawlspace or basement with the vapor retardant properly laid on the earth. The other things that a felt underlayment would add to the job are not needed when gluing and nailing. An installer does have to modify his installation practices but not to the detriment of the floor.

Gary,
NWFA also mentions nailing and gluing wide-plank flooring.

NWFA Installation Guidelines And Methods
Section III
Part VI
E. Wall Line Layout
# 13
For wide-plank flooring (5” or wider), to assist the nailing schedule of 6”- 8” and increase holding power, there are three options.

Option b. Apply an approved wood adhesive.

We have been blind nailing and gluing wide-plank flooring for many years.
Most older wide-plank floors we now sand and finish that were nailed but not glued squeak and have some movement when walked on.
We are starting a job now that will be blind nailed and glued. 3000s.f. of 7/8"x 5 3/4" antique heartpine.

Keep in mind Buddy, the NWFA is not THE authority on installation of hardwoods. It is an advisory association of volunteer members, many being manufacturers, distributors and contractors. I was an active member for many years and the NWFA advising gluing down solids is a recent recommendation. So, unless the manufacturer specifies it as a recommended procedure, the installer is on his own. It does appear to make sense though in most applications. And I am recommending this be done on most of my plank installs.

I like to glue anything over/@ 4inches. I just dont feel that the staples can hold that much width.