I think I'd try to keep the space between the crown and your border consistent. throw the level aside. You could mark a pencil line parallel to it. maybe slide a block of wood along the crown marking the pencil line under the block to result in a line that's parallel where the top of the border fits.
then I'd pin it in place or use masking tape if you think you can peel it without wrecking the border. affix it in place, see how it looks to you. the top will be loose and it'll want to hang away from the wall a little.
if it looks ok just glue the bottom edge, then smooth it upwards. it will want to crinkle along the top as it bends in sort of a U shape
take a razor blade and make relief cuts about 3/4 the way down and either tuck it under or relieve V shaped slivers everywhere you need to.
I was wondering if you might have success dampening the paper to try to get it easy to bend but you might rip it trying. if it were dampened you might get the paper to stretch a little on one side but you can't really shrink paper and if it stretches too much it'll tear or distort the gold printing especially if it is gold leaf and not printing.
If it looks really shiny like real gold ( think greeting cards) that is actually gold leaf that is applied under heat and pressure usually using dies. sometimes the dies also emboss, you'll see that done on greeting cards a lot. Gold ink is only so shiny, it won't have the same metallic look as real gold foil. the gold is very very thin. it has a glue on it that is activated by heat and pressure. I think it's the same stuff that you might see on an older glass door..
you can print with gold ink on a printing press but to get that real shiny gold one needs do that by letterpress operation. Letterpress is impact printing, think of john boy walton's press.. it would use lead type that is raised.
since it's a long continuous piece of paper. it probably isn't' printed on an offset sheet fed press. you can imagine how big the sheets would need to be! they probably have some special equipment that prints from a roll.. that's called a web press even though the web might only be narrow. newspapers and magazines and high production work uses web printing because it is very fast. The most common type of printing is sheet fed offset but they dont' go much over 80" in width so you wouldn't be able to order 10 foot pieces.
another press that prints like that is the ones they use to print on packing tape. it has to unroll and print the tape and roll it back up. you can imagine the noise that makes
if you wet paper it will want to stretch where it takes on water and stay that way. If you don't want to make relief cuts you could have success carefully dampening it and maybe use pins to hold it in place while it dries.
an example if you have a sheet of flat paper on your desk and you wet some part of it , you will see it want to stretch where it's wet. so that might work or you might wreck it , obviously it will tear easily if it's wet but you might be able to use a damp sponge and wipe along the paper to cause some controlled stretch then pin it in place until dry, then glue it on..
you could perhaps try this on some other long strips of paper to see how dampening it will make one edge grow and how well you can control that without tearing it.
Its probably expensive stuff. the place that prints it has specialized equipment, so other printers won't touch that which increases the price.
I used to fix machinery in places that do some specialty things such as greeting cards, wedding invitations and printing on weird things like matchbooks or napkins. old machinery is often used and sometimes it is customized to fit this sort of specialized printing. gold leaf and embossing is common in those places but not in most commercial print shops. It's very specialized work. gold is shiny but gold ink is only as shiny as the paper it is printed on. I doubt they'd use coated paper for the border. coated paper is the shiny stuff , like a magazine. when you see shiny printing on uncoated paper it is usually only on fancy things like greeting cards, maybe some packaging etc..
there is another process called thermography. in that process a powder is applied to the wet ink and vacuumed off. the powder is plastic granules and it is then sent through an oven to melt. You can get gold powders and this can simulate gold foil , it will be raised and if you look at the backside you will see the paper isn't embossed. the raise comes from the ground up plasic that is melted. You might see business cards with raised gold printing like that but I doubt if they'd use that on the border..
Ive seen other types of printing and you can immagine the equiment. one place that does bingo sheets ( each is different) had a specialized machien to randomize the numbering that used belts of numbers and it was a huge complicated affair. you'd see other types like the tickets that come in a roll for your door prize raffle, again somewhere there is a specialized machine to print that from a roll and it would have a numbering machine that advances the number and prints each time a different number..
anyway the gold leaf might not want to stretch at the same rate as paper.. that's sort of where I was going with it.
