I have some Galaxy hops (13% AA) in my freezer that I'm finally getting around to using in a single hop APA. I'm wondering how much I should use for dry hopping. I'm not sure how pungent this hop is. I mean do I want to use 14 g? 28 g? etc. Not sure how much is to much.

I've also been playing around with the hop schedule and would like some ideas. I'm basing the recipe off the APA in BCS. Adjusting for AA differences the hop bill is:
60 min - 19 g
10 min - 16 g
0 min - 16 g

(OG is expected to be 1.056)

Now that is a big difference in the quantity of hops for 10 min and flame out. The recipe calls for 14 g of each Centennial and Cascade for those additions. I'm thinking cut back on the 60 min addition and move more hops to the 10 min addition and flame out. I'm not sure how much though.

I've got 2 oz packages. So basically I have 4 oz to play around with, without having to open another package (not that I necessarily think I need more than that). If I use all 4 oz, great, then I don't have to vacuum seal the left overs. Not that sealing them is a lot of work. I just tend to be lazy.

Here's my advice. When adjusting hop additions to account for differences in alphas, don't bother doing that for those addtions that are primarily flavor and aroma. You aren't really looking for AA's from these additions (though you will get them anyway), you are looking for the contributions from the hop oils that typically aren't reported on the packaging, and as far as I know, don't necessarily scale with AA. Keep those additions the same weight-wise (for your 10 and 0 min), as reducing them to keep the IBUs the same will mean you may end up shorting yourself on aroma and flavor. So factoring out the IBUs you get from your late additions, adjust the bittering addition to give you the total IBUs you want for the beer.

I would also apply this same practice to dry hopping. If the recipe calls for 28 g of whatever, use 28 g of Galaxy, since it's the aromatics you want, and AA don't really factor in.

I have a galaxy APA recipe out there, it was part of my talk at the NHC this year (not sure if the presentations are posted yet) and I also gave the recipe to Brad Smith so you should be able to find it at BeerSmith. It doesn't use dry hopping, but it uses first wort hopping, hop bursting, and whirlpool hops. OK, it's not totally single hop, there is a little Cascade in there at the end too. But you can omit that.

Fresh galaxy has a big passionfruit character, which is great, but I kind of like it mixed with some other stuff. Sort of like Amarillo in that it has a fleshy fruit character. If you like an all Amarillo beer, you'd probably like all Galaxy. If you like your Amarillo with some Simcoe, try tossing some Cascade in with your Galaxy.

+1 on what Spider said.

Keep the size of the late additions the same so that the flavor and aromatic levels are comparable, then work your way backward to achieve the same bittering. If necessary, you can slide the timing of the bittering addition a few minutes either way, to hit your desired IBU target, too, rather than use some odd bittering amount like 0.57 oz. In a case like that, I'd add .5 oz and slide the timing a few minutes earlier to compensate.

Then, on subsequent batches, I will tweak the flavor and aroma additions to dial it in, always readjusting the bittering addition if necessary.

Hope this makes sense.