I agree on the one bigger ring being a spare. After digging into the carbs further I found:
- The float bowel gasket is pretty self explanatory
- One small ring goes at the base of the fuel/air screw. They have to be backed all the way out - THERE'S A REALLY SMALL WASHER IN THERE!!! DON'T LOSE IT!!!!
- One medium/small ring goes at the base of the main jet column
- One small ring goes at the top of the carb under the plastic cover.
- The second medium/smalll ring holds the needle assembly in the carbs, also under the plastic cover.
- The remaining large ring looks like it could be a spare to the needle valve assembly. It has to be, because nothing else in there is big enough for it to go around.
All of this matches the carb line-diagram break downs for where they should be.
After digging further into it, I'm glad I bothered to rebuild them. The rings were all terribly dirty and dried out. The one around the needle assembly, and at the main-jet base was real bad. It's no wonder at all that they leaked fuel into the crankcase. I found them on eBay for $67 shipped, too. Not bad for less than half price of what everyone else wants for them.
Hope this helps.