I once played a friends guitar from a German Luthier, Siggi Braun Fine Young Guitars, which had a mixed set of frets. Regular Jumbos (6100) on frets 1 through 11 and narrow Jumbos (6105) on frets 12 through 24.
While having the same crown height the 6100s have a wider width than the 6105s and the playability and feel, especially high up the fretboard was awesome.
Now my latest RGR620 came with a fret dress but them frets (being 21 years old) were already way down.
I found a young luthier here in Tokyo who just opened his own guitar shop and we discussed the mixing frets option and I let him refret the RGR620 with Jescar EVO fretwire (which I prefer over Stainless Steel) with the mixing frets option....I couldn't be any happier!!!!
Left of the 12th: 6100 size - Right of the 12th: 6105 size
BTW, we're talking lowest possible action, a flatout straight neck (no relief) and absolutely no string buzz at all!!!
And check out that Rosewood.....almost black!!!