Not sure about Scene Graph, but we had a similar issue. Firmware 7.1 makes video display resolution logic consistent across devices. Beforehand, it was actually inconsistent and matched the resolution of your _application_. So if you were in HD (720p) mode the coordinates and resolution of the video also corresponded to this. After the change, the coordinates and resolution match that of the _display_. So you'll need to translate the video coords, etc to display coords, etc.
app_display_size = GetDisplaySize()
roku_display_size = CreateObject("roDeviceInfo").GetDisplaySize()
x_factor = roku_display_size.w/app_display_size.w
y_factor = roku_display_size.h/app_display_size.h
dst_x = dimensions.X*x_factor
dst_y = dimensions.Y*y_factor
dst_w = dimensions.Width*x_factor
dst_h = dimensions.Height*y_factor
print "SetDest1 (" ; dimensions.X ; "," ; dimensions.Y ; "," ; dimensions.Width ; "," ; dimensions.Height ; ")"
print "SetDest2 (" ; dst_x ; "," ; dst_y ; "," ; dst_w ; "," ; dst_h ; ")"