Like you I have been finding crappies moving up over relatively clean bottom to the outside breaks, often hanging at the second one out from the weedline, generally later in the evening. Normally the smaller ones show up first, with the better ones, if they show up at all, often coming in at or after dark. They seem to be keying on relatively small structural changes, too, sometimes using breaks of only a very few inches depth or following a very shallow slot up. Often earlier in the afternoon, the area outside the weedline will have more of less resident dinks, where there is a dock to provide overhead shade. That seems to depend on available forage and often those crappies will relate to the sunnies that take up residence under the dock.