I think it would be best to look elsewhere. Apart from the fact that you are wrecking a perfectly decent bass, the fret job will probably cost you about what it would cost to buy a decent leftie budget bass, assuming you were able to find a luthier who would do the work for you... by the way, if you want a bass to play U2 material a fretted bass is what you want, I can't think of a single U2 song that has a fretless bass on it.