I like your original idea of weighing down the branches, though rather than attaching weights, I would tie them to long strings (make sure to use a loop, rather than tying the string tight) and attach the strings to rocks or bricks. Four branches would be idea, as you could get a nice symmetrical tree out of it. I've tied down most of my trees (close to horizontal) and in a few situations I didn't leave a central leader. Those trees are now relatively low (7-8') and fairly wide. Of course how big the tree gets will also be dependent on the rootstock.

Just make sure that it gets plenty of water during its first year. And you need to make some pruning decisions depending on the style of tree growth you want. (Central leader, open center etc) Mike

Granny Smith is a variety that is highly susceptible to a disease called fire blight. that is the number 1 disease problem for our area. The odds of growing apple successfully in Georgia go way up if you choose disease resistant varieties such as Liberty, Pristine or Goldrush. Here is a link to a UGA spray program that is pretty good that I follow for the most part. I suggest you start reading the Gardenweb Fruits & Orchards blog, you can learn alot from the site. That is how I got started, I now am growing around 50 apple varieties, all on dwarf rootstock. Here is a link that might be useful: UGA spray program

On the left of this pic is 'Glory' and in heavier shade will have a nice chartreuse/apple green color. Perhaps a bit more mounding than vase shaped. Sagae may be another to consider. Certainly vase shaped but coloring may vary based on light. tj