...there are two loopholes? 
Well, I'm counting the one-song rule in that.
Mine is 16 or so minutes. I considered adding one more song and decided against it, it's perfect as it is.
I should note that from the first two rounds, there's no correlation between submission length and scores. The lowest average scores have been at the extremes (the single long songs, and the shortest submission but that was nothing to do with duration), and everything in between has been averaging similarly.
Thankfully there are a few shorter submissions coming in now, thank you!