Hi, McGrath: Hmmm, never tried replacing steel strings with nylon on a steel-string guitar. Seems like it would be a pain to deal with loop-end nylon strings and a bridge designed for ball-end steel strings... unless one buys ball-end nylon strings in the first place. I'm thinking that one would have to be concerned about the nylon strings fitting into the slots in the nut, but since I've never tried it I don't know if that's an issue.

The main problem I see, though, is that nylon-string guitars are designed with wider necks (and a higher nut) for the specific purpose of accommodating the greater degree of vibration of the nylon string. If you put nylon strings on a narrower-neck guitar designed for steel strings, don't you get some buzzing or dullness of tone as the nylon strings vibrate against each other?