@ Crazy Vick - I thought about using multiple pieces, but the lady who sold me the frame, who has a great deal of experience and knowledge on the matter, highly recommended using just one piece. I hadn't thought about using wood with acid-free paper in between...are you aware of anyone that has done this? Has it held up?
@ Harry Caul - What size sheets would you recommend I use and how should I place them to ensure that the poster doesn't bend or collapse? The problem that I've encountered is that the largest size I've found in Toronto for acid-free foamboard is 40" x 60" ... my poster is actually 41" X 90 1/4". So, I don't see how I could use only two sheets (horizontally) in front, backed up by two more sheets (vertically) in back. Or maybe I'm just not seeing how it could be done.
@ Jayn_J - This very afternoon I started at King and Spadina, walked up to College, across to McCaul and down to King. I hit DeSerres, Michael's, Gwartzman's, Toose, Above Ground and the OCAD bookstore...I also called Curry's, Uline.ca, bagsunlimited.ca and Carr McLean...none of them had it.
@MoviePOsterBid.com - I found a few online stores that will sell and ship them to me in cartons of 25. Way too many. I eventually plan on putting up four or five 3-sheeters on my walls but 25 is way too many.
@ Erik1925 - $135 is crazy money for a sheet. The guy I found out in London is going to sell it to me for $39.95 CAD and he's going to cut it to size for me as well. More than likely I'll just bite the bullet and head out there to get it. It's just gonna be a pain in the a$$ stuffing it into my Prius and driving 2 hours down the 401 with this gigantic board literally hanging over my head inside the car. That's how I transported the plexiglass back home but that was only a half hour drive.
Thank you all for your feedback. It's much appreciated, as always.