I have seen them made with casting platforms. I thought about adding one to mine, but the way it's set up, if I were to stand up, it might tip the whole thing forward. I could probably set it up farther back on the toons, but then regular sitting would make it tip backward somewhat. Usually I just floated to a shallow area and stood up to cast.
As for drag chains or anchors, a 3 lb anchor would hold it pretty good except for on slick rock like the in the rivers here in AR. A drag chain is what I first used for an anchor and got rid of it for a claw type anchor.