Yeah, I don’t think I’d want to bother with something too large when it’s not the final product. 😄
I really don’t care what all it is as long as a 10-20GB down-convert is shared.
In terms of quality though, a higher bitrate is required to deliver the same quality that you would get from a cleaner de-grained video (like stuff shot directly to digital). If you were to use CRF for x264 in the range of 16-18 for the video I’d predict it would come out at a size greater than 30GB. Do keep in mind that even 40GB is heavily compressed.