Hello,
We use Swiper slider to create slider of the upsell products http://idangero.us/swiper/demos/
And unfortunately, when slider uses multirow view it displays items in the following order http://prntscr.com/h8aetm because it uses box-lines: multiple; and there is no way to change the order to show 2d product at the right side of the first product. That’s why what you have only 2 products you see it in vertical order. Custom CSS that Laranz provided breaks the slider width that is calculated by slider script, so, I would recommend you to remove it.
Regards