I had such trouble with the sleeves - which I didnt have last time I made this top. I used french seams for the first time ever, (using a book from the library for instuctions) and i also had to use bias binding around the shoulder seams (just dont look as it is not a pretty sight lol)
I made the top in size 18 months to 2 yrs, even though The Little Fella is only 13 months. From experience, if you are not using a stretchy fabric, you need to go a bit bigger for ease of getting it on/off. Also I wanted to play safe with the seam allowance for the french seams.
I am very pleased with it! (although I have no idea if it will survive washing lol)