Sunil and bigfrog :
I think we need to define what we mean in a pedastal seat . There are several types and especially heights. I have used the ones that are 1-2 in. above the bench seat and attach by a removable bracket over the bench. The are sold by Bass Pro and others including many boat stores. They do not seem to effect the stability of the boat. If you are talking about the high rise type found in many bass boats I would think they would make a small jon boat unsteady.
As we all know jon boats come in all sizes shapes and weights . The placement {location} of the front bench seat { the one first after the front of the boat} is very important in stability for sitting, standing or paddling. The shorter the boat the more important the location. I think most people who use small jons to fish in ponds fish from this seat than in the back. I like a 10 - 12 foot med. weight jon with a wide width and a short pedastal seat with the front bench near the middle of the boat. I want the boat to be level and stable in the water when I stand in front of this bench. ewest