I finally found some inexpensive ($15 for 20, including shipping) 3-amp 40v Schottky's on eBay. After installing my BZ mppt the performance dropped off a bunch in overcast weather (all summer if we are lucky, because of recurring droughts).
The cheap HF panels don't have blocking diodes, so when I hooked all the panels together, the shaded ones sucked up all the power.
After putting a Schottky on each panel I'm getting 25-40 watts in overcast and rain in the late afternoon. There is plenty of room inside the terminal connector box on the panel for a diode. I crimped solderless ring connectors to the diode and pop-riveted one ring to the positive feed cable connector. The other ring is screwed down with the panel's supply wire.
My panel's theorectical total is about 300, but the way they are mounted it's impossible for the sun to hit them all at once. They are on the ground and two outside walls because I rent here.
If the sun is out I can hit float at 7pm with no load in warm weather.
One of the HF panels failed. A crack in the glass kept growing until it now goes from top to bottom. If someone wants to experiment with that panel, email me dnix71 at yahoo. Since the glass isn't tempered, maybe you could cut it into smaller pieces and use those.
