I think it has to be done at the "interface level" In most DAWS, the Audio Config menu opens the interface applet, and you change buffer there. This tells me that it MUST be done at the interface, even though the DAW is the "master" and the interface is the "slave" (I say this because my particular interface has a "disable host control" checkbox, which implies the DAW is in control, as default) I hope I'm wrong though :) I could use a "128/1024" toggle switch :D