This may be a more involved modification than you are looking for, but you could just look into changing out the I/V resistor used in the MiniDAC. Pretty sure this uses the AD1955, and has a pretty standard opamp I/V, so should be fairly easy to find this resistor and simply replace it. True, you would be making a fairly large change, so should also change some of the LPF components, but nothing too radical.
Beta22 isnt stable below a gain of 2, right?
Off topic, but those Donuts doin OK for you?