I think he wants to simulate the look of the movie, not adhere to SFB/SFC specs. He is asking what he should use for the cylindrical phaser mounts on either side of the torpedo pod, with which Khan does so much damage to the Enterprise.
Don, that is a can of worms. Many folks argue that those are not high-powered phasers. The Enterprise's shields were down, and she was struck in particularly sensitive spots, yet she held up pretty well. If those were mega-phasers, why did a direct hit to the hull with no shields only penetrate a few feet into the ship? If those were such vulnerable locations, why wasn't the ship destroyed outright, or at least irreparably crippled? We've seen regular phasers do more damage before, though only in description. After all, the battle in TWoK is about the only time we've had a good look at exactly what happens when a ship is hit with phasers. Usually we just see explosions, either little blasts if the ship is damaged, or a big fireball if it's destroyed. Considering this, some folks maintain that the "cannons" are not mega-phasers, but are some sort of multi-directional turret. By this approach, the saucer phasers should probably have smaller arcs, say FA, L, and R, and the large phasers on the struts should have wider arcs, like FH or maybe FHL and FHR. Or possibly, the turrets might be designed to fire aft as well as fore, with the same arc as the torpedo pod. These turrets would probably be intended to compensate for the lack of a secondary hull with more phaser banks. To be consistent then, the Constitution class should have the same arcs for the saucer phasers, since both ships have the same configuration of phaser banks.
If, however, you really want to have mega-phaser cannons, you could use PhX's, which can be set to overload. All of the regular phaser banks then should be Ph1's. The PhA disrupts electrical systems, which the Reliant's attack does not seem to do. The PhB does more damage on hulls than on shields, maybe like carving it up as in the movie, but it doesn't look a bit like the film's FX. Both are heavy weapons, like disruptors, and require more power. As Age said, you might need increase the ships power, which would be odd, since it shouldn't have more power than the refitted Constitution. The Ph4 might be tempting, but, aside from draining the capacitor very quickly, it really is too powerful to be carried on a ship.