More on this later, but one obvious thing is that with the MSP430 using two diodes to drop around 0.8V off the panel, presumably to allow trickle charging of a normal battery, is that only 1.6V max charges the supercap. With peak charge Q = CV and supercap rated to 2.5V an extra 50% energy could be retained by allowing 2.4V on the supercap instead of 1.6. So the next mod will be to short out the 1N4148 and leave just the shottky diode, if I can confirm the resulting voltage will always be < 2.5.