Hmm...we definitely want to lean more towards the twenty minutes. We do need to include all dialogue, as well as our own little spin on certain events, and battles and the like.
Though we probably shouldn't set a specific amount of time. Some chapters, like the first, are relatively short, but others, like the one before the last, are pretty long...we will want to do the sidequests, I think, since they're part of the overall storyline.
We'll see. As I said, I'll need a couple days to think, and meanwhile you guys can get the rest of the stuff sorted out. (We'll worry about voice acting later. The essentials need to be done first.)