Several problems here. First, I was sure a half yard would be enough. Alas, the pattern is directional and it turns out his 5T tshirt I traced was maybe 2.5" longer than my fabric.
Second, I should have bought something for ribbing. I have an old red tshirt but it's faded.
Third, I just couldn't get the double needle to work right.
Maybe here it was because of the differences in thicknesses.
I found setting the tension to 5 worked the best. I think next time I'll do the neck like I did for th one hour pajamas or just zigzag.