How much beer volume are you looking to dry hop and for how long? I add 2oz of EKG to my IPA recipe once I've harvested the yeast (which puts the beer in the 45-50F range). A day, or two, later I chill it down to carb temperature (36-38F) and let that go for 3-4 days before packaging. I get really nice additional hop flavor and aroma out of that process. I can even let the hops stay for a bit longer due to the lower temperatures.
For reference, I have between 7 and 8 gallons in the fermenter for this. If you're going with 5 gallon batch sizing, I wouldn't go for more than 2oz the first time. You can always add more with the next batch. Better to want to increase it than have it be too much to enjoy early on.