Yeast food is dependent on the amount of yeast pitched. Using a full 5g of yeast in a smaller batch than 5 gallons is fine, you'll have a larger population sooner.
Spices might not scale equally, as some are more potent than others, such as cloves. You might not want 5 cloves in a 5 gallon batch just because you use 1 clover in one gallon.
Zman, I made that recipe and it turned out really nice. I do wish it would have either ended a little sweeter (mine went drier than I had hoped) or had more peach presence. Though I haven't had a bottle in at least 6 months. My suggestion would be to make it as a 5 gallon batch. I wound up with a 3 gallon yield after all the peach sludge. Also, make sure to use pectic enzyme, let it age for a long while, I had sediment drop in the bottles after bulk aging a year and it looked crystal clear. If you can, perhaps filter it.