Personally, I like to run no Machokes. Instead I run 4 Machops & 3 Machamps + 4 Rare Candies. Korrina basically means you can find Machamp and your Rare Candy in one go and evolve to a stage 2 right away, but that's a personal preference. The problem with that is if Trevanent is in play, you can't use your Rare Candies.
I also think Professor's Letter is really helpful for any deck, but especially yours because you only have 12 energy. As for your Ace Spec, I recommend Scramble Switch over Dowsing Machine, so you can switch Pokemon & multiple energy in the same go (again since your deck is on the low side for energy). Also your deck might run into some trouble with Pyroar and Latias EX.
I agree with running Palpad, simply because most fighting decks are reliant on Korrina.
You might also want to run Sacred Ash because of Juniper, and I would recommend having another Juniper over N, just because N is based on your prize cards. Consider Skyla as well, since she gets you your stadium & supporter cards that Korrina can't.