I tried knitting the smallest size with aran-weight yarn (I don't have the exact numbers of my gauge handy, but it's significantly larger than the pattern calls for), and the shoulders of my finished tee are just too wide. I've played around with gauge enough to know that this method of modification can be pretty hit or miss, and here, it's just a miss. If I was going to fix this, I'd need to significantly narrow the shoulders. Otherwise, I'm not too unhappy with it- I was going for a boxy, oversized look, but the giant shoulders just make it look sloppy and too big.
I'm not sure what I'm going to do with this yet. I'll more than likely end up frogging it. I do love the colors of this yarn, I just couldn't make it work for this pattern.
Ravelry Page: Psychedelic CYOAT
Pattern: Choose Your Own Adventure Tee by Allyson Dykhuizen
Yarn: Peaches & Creme Ombres and Prints "Psychedelic"