Galaxy can be a bit rough when used for primary bittering and its aroma/flavor is too good to use in that capacity anyways. I'd use something else to bitter with (columbus, magnum, warrior) and save the galaxy for your late additions. Also, I'd move the 30 min addition to something like 10 or 5 min, or save them for dry hopping. You'll be getting mostly bitterness at anything over 20 and nelson is really best used late in the boil.
Lastly, galaxy-nelson is an amazing hop combo (prob my favorite), although it can taste muddled in recipes that use lots of caramel and specialty malts. It really seems to shine in simple recipes, so keep that in mind. Good luck.