The L and R arcs are respectively original SFB 60-degree arcs that fire straight to the port and staright to the starboard. However, these arcs do not exist in SFC....if you try to use them they turn out to be 360-degree arcs in game.
Having these arcs implemented would solve a lot of philopshical problems and we would finally be able to implement true-to-life specs for Federation ships, for those of us who like to fiddle with the shiplists. For example, a TMP-era Enterprise-class starship has 12 saucer phasers: 4 port, 4 fwd, 4 starboard. This is easily verified by visual inspection of the actual studio model. However, the problem is this: the side phasers, if they are assigned the FLL and FRR arcs like they usually are, can fire directly fwd, which means all 12 saucer phasers can fire directly fwd, which makes the ship hideously strong. Also, there are an additional 4 phasers under the secondary hull that if assigned a 360 arc can also fire fwd, and so you have a total of 16 Phaser-I's or Phaser-X's (depending on what kind of specs you use) able to fire directly fwd. This in a nutshell unbalances the game, and so speccing a true TMP Fed becomes problematic, because for some TMP Fed ship designs, even Frigates such as the Knox and Daran have those 12 saucer phasers. However, if we have the L and the R arcs, then those side phasers can no longer fire directly fwd, and for ships that have 12 saucer phasers, only 4 of them can fire directly fwd, which preserves the balance more. You would also be able to properly spec the Miranda as well, which should have only the roll-bar mounted Heavy Phasers and the 4 fwd saucer phasers able to fire directly fwd, (along with the fwd torps), but with the present arcs if you give it its true-to-life 12 saucer phasers all 12 of them can fire directly fwd.....which makes it atrociously strong.
So how about it? Can we get the L and R arcs in an upcoming patch for OP? truth to tell, this is the one factor that has discouraged me from making a complete TMP true-to-life mod package for the game.