Re: Porch Pergola
It might be smarter to install a "yankee gutter" above the pergola attachment point. It's a custom-bent flashing with a gutter formed at the bottom. It would need to extend 18" up the roof, so it's under three courses of shingles. It probably wouldn't hurt to place ice & water shield above and below it.
And, really, if you had the yankee gutter, you could remove the existing fascia board and insert the pergola rafters in the cornice to the wall plate, and cut sections of fascia to infill.
Remove not the ancient landmark, which your fathers have set.