I've built three UJ's.........been tempted to put little skinny skegs on all of them. Even cut them out and had them ready to go on. Never got around to it on any of them and somehow survived this long.
Yes, they are a little like a tea cup at times, but a double paddle does make a big difference. If I had to paddle long distances, fast, i'd put one on for sure as it would pay for the drag and draft with the elimination of having to correct for direction.
But, they also make either perforations of a good boat necessary, or serious glueing to a snooth bottom. Bolting on with stainless or brass and a good fitting compound may be the best as it will allow the removal later for replacement after wearing it out, or changing your mind.
The best answer, of course, is to build a second pirogue and try it both ways. If you have any trouble with this, have your wife write to any of us and we'll back you up.
Piper