We have 8 inch wide live sawn hardwood that some installers are only recommending nailing down and some that are saying to glue also. They are concerned with cupping due to the width. Also, if we decide to glue, we have insulayment and underlayment, and they claim it can be glued to subfloor and hardwood. Any input?

Recommended practice is that you nail and glue wide plank floors 4" and up. The installer should be reminded that adhesives used for this purpose will
not perform their function when used in conjunction with a moisture retardant. Glue assisted applications will not be satisfactory
without direct contact with the subfloor. Meaning don't count on the glue to provide protection from moisture in the subfloor. The glue should be a premium grade urethane construction adhesive applied in a
serpentine pattern to the back of the hardwood