Setting an exact page width in Composition Mode.

Probably a bit of a random one, but I can’t be the only one who sets their Editor window to a specific width, and then has to struggle to rearrange the Paper Width in Composition Mode to get it to match up. Or, well, possibly I am, but it seems odd that you can specify a precise width for your pages in Editor, with only the sliding bar to attempt the same in Composition, and it often doesn’t match exactly the set width for Editor. Any chance, then, for a more accurate way of designating page width in Composition?