design scale

Am I missing something obvious?

So I have lets say two different products with different views in FPD. They both use the same design category and when I select the design it should replace the design in each product but with different scale.

Lets say one product is a tshirt and one product is a baby bib the view in fpd would obviously be different. I can't seem to do anything other than just replace the design in the product at the same size which means that when you select the design on the tshirt it appears much small in relation to the size of the product