My regular area is actually in the hub, on the north spoke of the hub facing the castle. I am always right in the back part of that spoke/isle/whatever. Just on the other side of the brick line from the circle path around the partners statue. And also standing on the right side of the railing.
Reasons behind that exact spot. First off, the center of the hub is elevated vs closer to the castle, the further you are back (but not in the walk way, the better view you get without the castle blocking). Standing on the right because the fireworks are off center towards the left so by standing on the right helps to center them a little more (still not over the center of the castle though).
Also, on the very first night of Remember, I was in that area (a little more forward due to a stage set up for filming) and I was lucky enough to talk with Steve Davidson, the shows creator for 2 hours before fireworks and he mentioned he designed the show to have the best viewing from where the partner statue is. So get as close as you can without getting in the walk way.
Also, after the show, be ready to book it, you should be able to quickly exit behind you from the hub and head towards Frontierland. Usually after the fireworks, they hold people there and let Fantasmic exit a little and then let people in from Frontierland so you should be able to snag a decent spot for the second show if you can make a quick exit from the fireworks.
Also remember,
Disneyland's castle is not as tall of Magic Kingdom's castle. Their castle size is to compensate for the lack of magic that park has.