When I started to worry about whether or not I'd have enough yarn, I got the sleeves knitted (most of one ball each, with enough left over to knit the neckband), then started the front, so I could at least be sure both parts of the body were the same length and the sleeves would be comfortable. Now it's just a case of continuing both back and front to keep them the same, and remembering to do the neck shaping. I should be able to do another 4 pattern repeats (48 rows) back and front, maybe 5, so it's not going to be a crop top, but I'm not sure if it'll get to hip length. I guess I'll find out...