I read what you are describing in Dick Raymond's Joy of Gardening. He planted an ounce of seeds mid July (3-4 months before killing frost is expected) in a 3x5 foot area and ended up with 45 pounds of sets.
SOS

I just purchased 3 bunches of onion sets and we now have 6 inches of snow on the ground. I put them in a plastic tray with a few drops of water to keep them moist. I put the tray in the refriderator in the garage for a couple of weeks until they are ready to plant. I figure they store them this way in the green houses so it should work. Any good tips from anyone out there? Thanks.