Sorry if this is a repeat question. I have come across a lot of differing opinions on proper install standards. Proper install methods seem to vary by region. Hopefully someone here can set me straight.

I live in Illinois and am installing 3,000 sq ft of Bella Cera 5" solid Hickory floors on 3/4" plywood subfloor. In the past I have used a vapor barrier and nailed, no glue. My understanding is that 5" is starting to get into the width of board that should be glued in addition to nailing. I have been told by a retailer that I should just use liquid nails and glue strips every 6" or so perpendicular to the flooring to glue it down. Troweling buckets of urethane adhesive on the whole floor sounds like overkill (and expensive). I have read on other forums that liquid nails should not be used. It is too rigid. Is this accurate? Is there a recommended adhesive that comes in a tube? Or, should I abandon that technique altogether and trowel on the more expensive urethane stuff?

Thanks in advance for any suggestions.

Latex sub-floor adhesive holds well, along with the fasteners, and is not brittle.
A urethane glue will work, too. Some urethane glues etch a pre-finished surface, so be careful.
Nail or staple every 6 inches, with a cross bead of glue every 12 inches, and at plank ends.