Oversized Classic Shirt?

I have some white, kind of windowpane checked double gauze. I'd like to make a slouchy Classic shirt with it for summer. What's the best way to make it bigger without looking too sloppy? I'm kind of chesty for my size and sometimes slouchy ends up looking like maternity wear if it hangs too far away from my body. I LOVE the Classic shirt pattern and I've made tons of them, but they are all fitted. Is it best to keep it fitted through the shoulders and bust and just upsize the sleeves and torso a bit so I don't look like I'm being swallowed by the shirt? Also, I have not ever sewn with double gauze before so any tips would be appreciated!