First mistake was using the extra small oysters we got at Costco. They shrink up to 1/4 of the raw size. None fell through the grill, though. I just set one grill rack on top of the other at a 90° angle. Seemed to work well enough but a rack designed for small food would be better.
I marinated them for 24 hours in a brine I found on the web under something like "Best Darn Smoked Oyster Recipe!".
Rinsed them off and put them on at 225°. Checked them after an hour and they were almost there. Got busy doing something else and failed to check them until another hour had passed. Over half of them were indian candy and the rest were well done.
They're going in the trash. I don't like the taste and neither do I care for crispy critters. Waste of a good quart jar of oysters. Next time - stew.