If your mobile design has more content than the single screen, do you create multiple mobile containers or stretch it?

If you have to show more valuable information, I think is good to have more then one mobile container. In this way all the information and photos will be more visible then in the case of shrinking everything just in one mobile container. For example if you have to wireframe a website that sells t-shirts: in first mobile container you will show how the first/main/home page looks like,
and in the second mobile container you will sketch how a selling one t-shirt page looks like. Hope I've been helpful :)

I think your question is related to responsive web design - Usually you would go the route of Mobile First, this means you start off by making the mobile version first. This usually only includes the most basic features and not everything your main website would. As Raffael said you would either hide most content behind a menu (like a hamburger menu), or you would just shrink it down and make them have to scroll down.

On concept is a onepager where you scroll down the page till all content is displayed another methode is a menue with links to your other content with the same layout. Was that your question ? ^^

If you are designing a mobile page and the content is larger than the screen height then I would increase the height of the mobile device to stretch until it suitably fits your header... all your content and your footer. Having lots of mobiles would waste space and clutter your design.