Tennessee, Welcome to GB's, good place to be.
Congrats on the BC and upcoming mods. Want to see Lee's work? This was mine, and I'll vouch for Lee's work anytime. The sight he saeels on Ebay is better than the one I had and it (mine) was excellent.
How's this look to ya?
He does very nice work and it's not as expensive as you might think.
Check Here On your other note, there is one fellow here using a Williams FP with BP in the 45-70 pushing, I think, a 500gr to 600yds, and the sights covers it, so I think the 45-100, ought to go "a mite farther".
But you wont go wrong with Lee's sight either. He is very experienced in the fine art of gunsmithing and shooting BPCR.