I know this is not recommended. Does anyone use the large cast iron grid on top of the adjustable rig? If so, do you ever have trouble with it sliding? I have bought one but I haven't used it yet. I have the spider, but the one for it is only 13''. If I needed to cook more than two steaks at once seems like the large would be a better way to go. you also could cook several hamburgers or other things on it. I don't want to buy both, but if I should just keep the large I would like to use it on top of the rig to get more use of it. What are your thoughts on this delemma? Also, what are your thoughts on a cast iron grid in general? This is my first post. Any help on this would be appreaciated. Thanks.