Are you worried that the boat will be so light that it will not rest in the water down to about the lowest step and instead sit so high out of the water that it will flop from side to side?
I'm not so sure that would actually be a problem. Flat-bottomed boats generally have a very stiff rolling motion, whereas rounded boats like a sailboat will roll smoothly and gently. In your case, if the boat does sit too high, it will begin to roll softly like a sailboat, but as it gets into a steeper roll angle, the resistance will sharply increase when the 'outrigger' part of the hull enters the water. It might give a funny ride, but it won't flip over.
In the marine industry, even those who are design engineers cannot rely strictly on calculations to determine the stability of a craft. After all the calculations are done, they still do an inclination experiment to determine the stability after everything that is normally part of the vessel is on the vessel. This experiment involves moving a known weight a measured distance from side to side and then reading off the angle of inclination.
Are you worried that the boat will be so light that it will not rest in the water down to about the lowest step and instead sit so high out of the water that it will flop from side to side?
Nope...hadn't even considered that actually.