Pokemon - 19
3-pokemon reversal (now catcher)
Trainers/supporters - 31
Energy - 10
With catcher, you'll want another magnemite and depending on much trainer lock there is in your area, you may also want a second magneton. I find that a single pachirisu for energy acceleration is more than enough, because once you use it, it becomes a dead card. One more horsea would ensure that you're able to see a kingdra come into play as well. I like a cleffa in the deck just in case my starting hand is bad or in case I need to stall at some point later in the game.
I don't have any changes to suggest since 10 energy is typically enough for magnezone as long as you rely on your yanmega primarily for KO's.
Now that we have super rod, I'd replace the flower shop with it. For consistency, I like to max out the pokemon collector to increase the chances of starting it on the first turn. Since yanmega can take fast prizes, I typically don't run twins at all in the deck, however, if you like, running one may help. The supporter N really works well in magnezone based decks, so I'd consider dropping a some of the copycat for it. You should still be able to easily match your opponents hand size with it.
This deck was submitted several months ago, and while it may have taken me a while to review it (I wanted to do a video review of it), it's still a viable deck. It's lost some of it's steam due to the increased number of electric decks (yanmegas weakness), however, since the meta in some areas seems to be constantly changing, it could still be an excellent deck to play (and as some have proved, can still win tournaments).