By what you describe, I don't think hard-paning is the recipe - as k3wl as it may sound on standard doubled arrangements.
When you say the second git is harmonizing, does that mean it's following the same line, just harmonizing by adding the third or a fifth or something, or is he playing his own little fills or mini riffs, related to the lead line in harmony only?
I'd look at three options to try out. First, leave the lead center, and stack the #2 git right with it. This would probably be the most effective if git #2 were indeed doubling partial lines, and doing it at points in the #1 riff that benefit form being accented like accenting the syllable in a word. It would be similar to the trick used on hip-hop vocals (I know you headbangers hate to hear that...except for Kid Rock

) where the second track is adding emphasis to the first on a particular word in order to emphasize that word or to give an extra cadence to the rhythm of the track.
The second option would be to move the lead git just a tad off-center, say 10% or so either way, and throw git #2 in symmetrically at 10% the other direction. This is a robust option as it does let you have some seperation betwen the gutars, still sounding pretty cool, yet the lead git is not far enough off-center as to be mentally noted as anything but pretty much in the middle of the mix. Additionally this can still provide enough room in the center for the lead vocal to shine without constraint.
The third option is arrangement-dependant, but it can work well, even in metal, if the relation between the vocals and the guitars in the arrangement are right. This would be to symmetrically pan the lead git and the vocal, one somewhere around 25% L and the other around 25% R. This works best when both are prettty much full time, so you get a good overall balance of energy between the two tracks. The fill git placement would depend a lot upon it's function as I asked about in the first paragraph; that can go down the middle, or, if it's a fill part where the vocals are fairly voing, you can pan that to around where the vocals are.
Remember, mixes can remain fully symmetric-sounding and down the middle without actually having to pile everything up on the center line of the stage.
G.