The answer depends on what resources you have available.
I am a communications pro and use many different packages, most
prominently CorelDraw! for this situation. It allows you to scale
drawings that are only limited by the size of the output of your service
bureau. If you don't regularly use a SB, I am sure one is near, and the
quality of their work is climbing quickly while the price is plumetting.
For example, for the last ACS MARM show, i was able to produce a full
color poster of our product line in tabloid size (the service bureau
using a contnuous feed paper, can generally give you quite a length.)
All for $15 US and shipping - they are located in the next metropolis.
Lacking the desire to do this, there are a number of products available
to what you want, but cutting and pasting is almost a virtuale must.
The upshot is, CorelDraw! will allow you to customize the size required
and prevent the shoot-down. You will still have to back it with some
good backing (I personally like artist make up board, not too expensive).
Hope this is of some help. More if you care to e-mail me
west at arsoftware.arclch.com
-->the black hole people