Hi Dan,
The Intensity Shuttle requires a great deal of bandwidth, and I would expect the USB 3.0 chip on current laptops would not supply sufficient bandwidth to support two.
The driver itself can support multiple capture devices. Using two or more devices is quite common for development of specialist applications, but I think this kind of thing would be quite difficult on a laptop at this time.
If you need any further help please feel free to contact your regional support team, and they should be able to help you out. Please either use the web form from the product pages in the support section on the website: https://www.blackmagic-design.com/support/ , or using the phone numbers on the following page: https://www.blackmagic-design.com/company/.
Chris Pearse
Technical Support Consultant
Blackmagic Design