They’re stable enough for athletic people with balance to do a number of very inadvisable things. They’re not so stable that I would want my grandfather with balance problems trying to stand on the deck while I move about the boat.
The Classic Highsider (15’4″ model) is a poor choice for a poling platform; everyone I know uses a cooler. This is because the transom is too narrow. However there are several larger models of Gheenoe which are plenty stable enough for a platform. The full blown LT25 model is stable enough for a center console and an elevated front and rear platform.
My main beef with my Gheenoe is that the sides are low enough that it is not really a safe open water boat, including lakes, unless no other craft are around. If you’re wanting to be out on Lake Lanier look more towards the Carolina Skiff.
For marsh fishing, the Gheenoe is almost ideal. It is also an ideal project boat. I have a truly slick boat with less than $2500 in the whole thing.
Mike Anderson knows more about boats than anyone I know.