I switched to the tired 12 V trojans, and got a good 20-30 minutes of playing. The load I used was the same plastic oven as the other power test but the nichrome ribbon had broken. Not very safe.
The 10 diodes are each dropping nearly a volt each, which seems to be limiting the maximum voltage.
More experiments needed, but the circuits are working. I got up to 13A and 145V.