How do I smoke large oysters?

Oyster season is on and I have been gathering oysters most everyday. I had some smoked oysters that were super large from a seafood market once and they were great. Has anybody that fools around smoking fish and fowl ever had good luck smoking large oysters and how did you keep them from sticking or fallling through the grates? Maybe par boil first? I tried leaving them on the half shell and that did not work well. One side was smokey and the bottoms were white and stuck to the shell even with very low heat in the smoker.