a question for submitting lowerthirds in motion graphic category

hi there, here is the deal, i want to submit a lowerthird pack to the motion graphics category, my question is on the resolution.

the lowerthird would be full hd resoluton but i need to upload 1920x1080 or i can upload just resolution where the animation fits like 1920x420, or i need to keep the black space in the 1920x1080 resolution?

thanks in advance