Am finally ready to install enginered flooring, 5" wide BC over crawl space. Would like the experts advice, should I put down felt paper and staple, or no felt paper and glue and staple?

Had an idea. I have to put 1/4" plywood over osb subfloor for height reasons,how about putting felt paper between those two layers, so I could still use glue if I wanted to, and also have the felt for a moisture retarder?

Sounds like a plan. Make sure your crawl space is DRY and well ventilated. It must remain dry all year round. Many manufacturers require a 6 to 8 mil polyethylene moisture barrier placed on the ground in the entire crawl space, even for engineered. By gluing and nailing, you will be insuring that floor will not snap, crackle and pop. You could forgo the nailing if you wish and just glue it with the factory recommended adhesive since you will be installing a 1/4" underlayment. Ensure your underlayment is well stapled and FLAT.

Thanx Gary for your response,will go ahead and put felt paper between subfloor and underlayment, and glue and staple. Only 150 sq. ft. so no big deal. Already have vapor barrier on ground as you suggested.