I recently purchased a 15' Johnsen type skiff that I am starting to rebuild. I want it to float as shallow as possible, but I do not want to power the boat with only a 10 or 15 HP. The build itself is going to add more weight than I would like, so I was thinking about adding sponsons. Has anyone checked their draft before and after adding sponsons? If so, how much difference did they make? Any feedback is appreciated.