I would live with the 80 watts, and use the money for more panels.
Then turn you attention to getting the idle current down a bit more.... try bigger inductor, and when that fails.....more turns on the transformer to get the flux down, and so less magnetising current.... may need only ten or so extra turns on the secondary and primary to match, and the flux drop off may be enough to get you in range... ie more copper loss, and less iron loss.
Copper loss is only when you push it, iron loss is all the time.
For testing this out, just hook up wire will do, as you are only interested in the idle currents, and that will beonly 1.6a max on the primary, and nothing on the secondary.
If you are daring, you could simply change the staircase resistors ( bypass some) and this will get the voltage down say to 220 or 200v to test how well/much the flux change needs to be.
Complicating a simple system is the last resort....... I just would find another way.
..........oztules