What about split-tourneys, where the better player were put in one group and the lower rated in the other one. In this wy you can fill up the tourneys quicklier and the lower rated player must only play at the final against a higher rated player 😉
you really shouldnt be worried about whether they are cheating or not. The purpose of playing chess is to get better. To improve your game, sure you might run into a few cheaters, but thats life. But anyway, we are getting off subject.