Hey - I just knit a sweater!

I sat down with a 4.5 mm crochet hook tonight and ended up with a finished sweater: (Making do with a bathroom mirror reflection photo as nobody else is around to take a picture right now) Overall, I am relieved that it fits happy with the fit post blocking. However, I'm not sure about the neckline: The pattern instructions are to do a row of single crochet, but I am toying with the idea of ripping it out and doing a few rows of garter stitch, or at least another row or 2 of crochet. Since the sleeves and bottom of the garment both have a 1 cm garter border, the single row of crochet looks kind of skimpy to me. Any suggestions/opinions would be appreciated. One minor problem is that I used the leftover charcoal yarn as the contrast colour on my Twisted Vest, and I don't know if I"ll have enough to complete the I-cord and arm/bottom edging. Why do I so often find that projects intended to use up leftover yarn leave me having to buy another skein of the "leftovers"?