Im working on an attic insulation project at my home. The roofers used way too long of nails when they roofed the home last and the nails are everywhere sticking out about an inch. Before I insulate, I wanted to install the plastic air vents between the trusses to allow for air flow from the soffet vents. This was impossible do to the huge number of nails poking through. My trusses are spaced 24 inches. I decided to install 24 inch wide by 48 inches tall pieces of hardboard attaching to the truss. It took me 3 days and I installed them all. It looked great and gives much more air flow than the typical between the truss plastic chutes. 2 years later I crawled in the attic and the hardboard has "sagged" about and inch in the center over time. the hardboard is still hard, but just sagging. Each piece of Hardboard is attached with 4 short drywall screws.
My question for you is:
Should I install some perpendicular 1X3 strips to keep the hardboard from sagging further? will it sag even more over time if left alone? Will hardboard eventually decinigrate and deteriorate? How long do you think it would last? Should I add more screws/nails? Any other ideas for my situation?
Please see attached images.