Both Hellgate and SSA have done what is common in the adjustment of the rear sight as it exists. In the years that I was working in the gunsmithing business I had a fairly hard and fast rule in the removal of metal: "Work on the lest expensive part when removing metal.". (i.e.; replacement of a dovetailed sight: remove metal from the sight, not the barrel's dovetail). In the case of BP revolvers, the cost of a front sight is low compared to the cost of a hammer, cam, roller and pin. With that said, if one is aware of their skill level in working on weapons, and goes slowly in the removal of metal from them, they can do a good job with some standard tools. One tool that I ALWAYS caution not to use with this effort is the Dremel Tool. It can, and has, done more damage than good in all but the most prudent applications. Small hand files and such are far more forgiving in their attack on metal parts.
I recently removed a slight amount of metal in the rear sight of an ASM '51 Navy that shot left. I used Swedish needle files to "move" the rear sight to the right. Using a square file, I was able to effect the correction. In my case, this was a good thing as my eyes are not as good as they once were and the greater opening allowed me to see the sights better. A slight benefit from the operation. Further removal of metal in the hammer nose would have proven to be too much, and would create a sight picture that would have been unusable in common application.
Thoughts for the day: A front sight costs less than a hammer and it's componants. It can be fitted without too much effort. It is far easier to file it down and can be replaced if one does go too far for less. It is also much more forgiving if one is new to this work too. A mistake can, in effect, cost less and be corrected quickly with another sight up front.
In the long run, the decission on which part to adjust is up to you. If you feel your skills are more than up to this task, go to it and fix your problem. If one feels a might skiddish in removing metal form their firearm, then take it to a compentant gunsmith and have him do the task (and it he messes up, he'll eat the cost of the replacement too!)
Good luck on your effeorts,
Wade