The idea about posting the riddles themselves in a seperate locked thread sounds like a good one.
Or just link to each post in the OP containing a riddle when it gets posted.
And I wouldn't worry about the flooding in. If you only choose to check out only once or twice a day, then that stays your choice. I like the way the previous contest was held, and the flooding issue isn't a problem because you don't need to check
all the posts, do you? You check out the riddle (assuming it's in a seperate thread for better overview so you won't try to look up answers to riddles which were already solved), then provide your answer(s). That's basically it. If people posted the same links already before you did, that's that. The only ones who
might get a hard time are the mods. But seeing how especially the AS team should have a slight advantage in this contest, some mods are bound to participate and are thus able to keep things under control. Though I doubt besides the amount of posts itself there will be any more problems.