Poster Format Vs Other Products Format

Hi Spreadshirt
I’m really excited about you have added posters to your list of products. But why can´t I scale the image on the poster product smaller after uploading! For all other products it is best to have the print design as close to the image edge as possible because the print design cant be scaled outside the print safe-frame. For posters I want more “negative space” around the design motive but if I do that the design will be to small on all other products.

So my question is:
Is it possible to link my uploaded “Poster Design” to the uploaded “Normal Design” ?

That way i could have a colored background on posters and transparency on other products but avoiding dubbed designs in “All designs”

Also will you ad metal signs to your list of products in the future?

Thanks for a great service
Casper