You have to edit the EG1 release value for ALL regions in the instrument editor.
Get the sound up in GS edit and zoom out on the keyboard graphic window far enough that you are able to \'rubber band\' all of its regions.
Now when you edit you are editing every key on the piano. You can type new values for EG1\'s release time into the window next to that parameter name, or use the graphic blue line near the bottom of the regions (drag and click).
If you hear no change, you must choose Apply to all regions to have your parameter come into affect (in some cases).
Don\'t forget to \'save\' or \'save as\' when you\'re done.
Soryy if this description is a little loose - it\'s past my bedtime
FWIW, I have the Boesendorfer - I haven\'t used it a lot yet, but my impression so far is that it\'s great on the bass end, but the treble end is very disappointing. The hammers were badly in need of voicing; the treble notes die out *very* quickly. I don\'t think you\'ll be getting any nice singing melodies out of this one (unless they\'re in the bass!).