The best alternative is not to ask here for help when you admitting to pirating movies. Figure it out yourself. This forum is not for illegal activites
You won't notice much difference. Most 1080p files that have been compressed into MP4 usually are in the range of 1.5GB to 3.5GB. The same file in 720p is going to be less than a gig. I can fit up to 8 MP4 compressed blurays in 720p on a blank DVD.