Solar Power really is the only way to go for me. Charizard is dying fast so might as well go full power with that sp atk. Solar Beam also covers some of Charizard's weaknesses, and Air Slash is surprisingly good, I love that flinch rate.
Solar Power Mixdard was surprisingly good in the early days of BW on my Sun Team.
I would love to use Solar Power Mixed if Dragon Dance was legal with Solar Power. The better part of Charizard's movepool is physical, so it supplements Fire Blast extremely well, and the speed increase is really nice from Dragon Dance.
Unfortunately it's not, so I stick to Solar Power Special. --- Not changing this sig until we get a new main series Tales game released on a Nintendo console in the US