[*] Now the MusicXML files are loaded of version 1.0 and type "score-timewise". So, you can now open .XML files exported from the "Guitar Pro 5". An example file "Chuck Berry Style.xml" added to "Exercises" directory. Unfortunately, "Guitar Pro 5" exports all notes on only one (tremble) stave, and does not keep information about their grouping, slurs, etc.
[*] It became possible to change the clefs not only on the boundary of the measure. Example: 22nd measure of the file "Rigodon.mxl" from "Exercises" directory.