Posterhanger.com Update:
I exchanged a few emails with a gentleman named Steve Naughton at posterhanger.com, and he showed me how I can hang the 84" 1949 poster using their product. My order has been placed, and, if all goes as planned, I'll be combining 40" and 44" poster hangers with a special connecting piece to hang my poster. It cost me a few $'s, but I feel much better knowing that I won't be applying adhesive to the poster. More to come after the order arrives and I try the product.