Book Export to JPEG

I'd like to use the Book Module more for exporting JPEG spreads so I can then upload them to a publisher, like Kiss Wedding Books. I'd rather use LR than InDesign because I like being able to edit the photos right there.

The problem I'm running into is that LR is trimming off pixels on export. So, a  12x12 page at 250ppi is not 3000x3000, but 2968 x 3000.

Anyone know anything about this?

Thanks