shirt from skirt

So I made a shirt out of an old skirt this evening. I took a t-shirt that fits well, pined it on top of the skirt (bottom to bottom), and sewed around it. Then I tried it on, modified, tried it on, modified, and so on until I got the above. It ended up pretty neat, because the pockets are up near my shoulders and the skirt's zipper goes right up between my shoulder blades. While it looks a little less than professional, I sort of like that about it. It gives it some energy.

Now, while it turned out pretty well, I had a problem with the sleeves. I've been making shirts out of other things for awhile, and always have issues when I get to the sleeves. They're usually either too loose or too tight or at a weird angle or whatever. Tracing t-shirt sleeves is not enough - they have to be their own pieces. Does anyone have advice?