When I lived in Scotland I did a great deal of flyfishing from the float tube, mostly at Haddo fishery north of Aberdeen.
I got into flyfishing for Pike from the tube on some of the lochs on Speyside, around Aviemore. It's a very effective method but it can be hard work in the float tube on some of the larger lochs, your pontoon boat would be easier,
There were a couple of very good lochs on Deeside, inland from Aberdeen. Unfortunately all of the sizeable Pike were removed by Eastern Europeans who worked in the fish processing sheds in Aberdeen, Peterhead and Fraserborough. My personal best pike of 29 lbs. 12 oz. came from one of them, unfortunately not on-the-fly.
Here in France I've float fished and fly fished for all sorts of species from my float tube but unfortunately no pike.
I would be very interested to hear how you get on.