We have ordered extra huge oversize rag (or maybe consv. board) from Small Corp. It needed to be trucked in and the shipping was quite reasonable. I think they can quote it ahead of time. I think we had to buy 10 sheets also. We only needed two for that particular job, but we have since sold a few to other local shops.
The best thing I ever learned from Paul MacFarland, was to use screen door bead for spacers. Not the "reeded" type, but the flat on one side, "bull-nosed" on the other type. It is about 3/4" deep (I love the look) and the perfect width (just under 3/16".)1/4" deep is not enough in my opinion. You can paint it to match either the frame or the backing behind the artwork. We either glue or supersticky ATG it to the frame with the curved side facing the frame. I buy it 100's of feet at a time from Home Depot or someplace comparable. Also, it works best if you can cut it (miter) on a chopper. A razor blade ain't gonna do it... If you would like me to draw a picture of how we put it in a frame e-mail me and I can send a pic to you. (edie.artetc@juno.com)
Also use LOTS o'hinges on that puppy. (not filmoplast, either
) We use a fc backing behind the rag board on which the art is floated and the two are bonded together. (dry mounted or SS ATG'd) If you don't bond them, the rag board with the heavy wc paper hinged to it will "flop" forward, especially when you use spacers that deep.
And even if you use a big mama frame, be prepared to use a strainer frame inside, as
well. We drill holes in the strainer frame at an angle for screws to attach it to the inside of the frame. (I can send you a pic of this as well)
And we will also sometimes use metal corner plates just as insurance to hold the strainer in the frame. And we put the hanging hardware on the strainer frame. D-rings (NO WIRE ALLOWED!)
Also, try not to get involved in a "rush" situation on a piece this size. Unless you're REALLY LUCKY...
The Goddess has learned the hard way not to tempt fate in this way.
Good luck!
(ps- if you e-mail me, I won't get it until Monday-- I am on a computer-free junket [how do ya like that one MM???] this weekend.)