Large Mounting - 77" x 100"

drop back 5 and punt?

rising makes a mat (#401802) it's a warm whit rag that's 60x 104 but thats the biggest i've ever seen.

short of any thing else I'd say cut it, mount it and then splice it back together again.

From the business point of view my sales pitch would be to cut it a frame the two halves as a dyptich.
What in the world are you, or the customer, going to do with it if/when it's mounted?

I don't think one of those little plastic sticky hangers will work.

You can bet they'll come in an Austin Healy Sprite to pick it up.
And how will it get into the house,

and over the fireplace vaulted ceiling?

Blue Cross of Michigan once ordered a 48 x 96 vac press for their art department on the 17th floor. It wouldn't fit in the elevator
Also make sure you can get it out of the door of your shop.

I did one this large about 5 years ago. What a pain.

Is the poster of any value?
Mine was an old advertising poster that the client paid $12,000 for.
We built strainer, backing, poster, acrylic package and sealed it with heavy duty clear packing tape. The 4 rails were designed so that we could bolt them together at the clients home.
The whole thing weighed about 200 lb. and was hung with z-bar. It still looks great and has held up well over the years.

The client has had the room painted and the painters moved this monster with no problems.
We can get it out the doors, that not a problem. We can also get it into his home. This poster is a B/W graphic from an Abercrombie and Fitch store display. I think I going to mount it on a joined Luann panel with paste. It get a large black frame.
Sorry about my English in the last post, I've been drinking too much spiked coffee trying to figure this one out. Hic!!!!!!!!!!!!!
If you are going to use the 1/4" Luann "door skin" panels, you'll need to build a fairly complex cradling system for the back. The Luann tends to warp out with the smallest amount of humidity. Were you planning on sealing and filling the panels before mounting so the grain doesn't show?

Another option would be to have one of the poster conservation services mount the poster to a linen/cotton fabric, and stretch it over a frame. I don't know if this is bigger than their capability, but I have seen some monster posters mounted this way.