The only problem with doing a small batch in a large carboy is the percentage of liquid lost during racking is fairly high. It is more of a problem if one were to do a 1-gallon batch in a 6 gallon carboy, but you should be just fine. This is a minor problem anyway.
Recipe looks good. Normally when I do small batches, though, I do something funky with it (like add a bunch of dextrose or something). by doing weird stuff to small batches you may end up with something weird, but a lot of times I'm surprised by how good they turn out, proving an accepted theory wrong. Small batch experimentation has broadened my brewing horizons.