[Andy]

Here's an unsupported patch that detaches the 3D window and should allow it to be dragged into another screen.

EDIT tcl/ac3dview.tcl and FIND:

proc make_views {} {
global viewsetting copycontext
global frame ToglWinName
global prefs_share_opengl_contexts

# MAKE THE 3D WINDOW


frame .views.xyzframe -bd 2 -relief sunken
frame .views.xyzframe.f
pack .views.xyzframe.f -fill both -expand 1
togl .views.xyzframe.f.win -rgba true -double true -depth true
pack .views.xyzframe.f.win -fill both -expand 1
set frame(xyz) .views.xyzframe
set ToglWinName(xyz) .views.xyzframe.f.win


REPLACE WITH:

proc make_views {} {
global viewsetting copycontext
global frame ToglWinName
global prefs_share_opengl_contexts

# MAKE THE 3D WINDOW

toplevel .test
wm title .test "3D"
frame .views.xyzframe -bd 2 -relief sunken
frame .views.xyzframe.f
pack .views.xyzframe.f -fill both -expand 1
togl .test.win -rgba true -double true -depth true
pack .test.win -fill both -expand 1
set frame(xyz) .views.xyzframe
set ToglWinName(xyz) .test.win

Let us know if it works on your multi-screen setup.
(remember to keep backups...)

Andy