Have you worked this out yet? Blipfoto publishes everyone's blip in the same size frame but the crop style affects how they fill that frame. Resizing your image will have no effect on the size shown. I submit mine all at full size incase Blip ever reintroduces the printed books where high quality is needed. At times when the internet is difficult I resize to 1024 long enge for quick loading.
Was your entire screen magnified at the time?