So4M has a good point about the newer engines.
My experience with seaplanes has been that they are hard/impossible to get up on the step if they are too heavy for the hull. Adding width to the hull as you indicated will support more weight, but the smaller engines and modern radio stuff are lighter.

Adding chines (1/2" triangle stock) along the edges of the bottom will contribute to a lot of initial lift and pop it up on step, too