Hi Jay,
Just wanted to update this thread with the information from your support ticket.
The Default Product ID setting does not support multiple instances of the Product Details module for Products configured with Variants. Currently a Product with Variants needs to be navigated to from the Product Listing page.
To remain on the Product Details after clicking "Add To Cart" the built in MiniCart or MiniCart module can be enabled in the ProductDetails module settings. More infor mation about the Product Details settings and Mini Cart options can be found in the KB article at the following link:
http://helpdesk.smith-consulting.com/...
Thanks!