Reserve buoyancy in a small open craft, where to place?

If you need to know more about how to calculate how much flotation you need and where to put it go here Boat Building Regulations | Flotation https://newboatbuilders.com/pages/flot.html Pick level flotation if you want the boat to float upright, if you just want it to float choose basic flotation. You mentioned putting flotation in the lower part of the boat. This can cause a boat when swamped to roll over and float upside down. If you must put some in the bilge leave a space down the center. This helps to balance the buoyancy of the so the boat doesn't roll. A good place tot put flotation to keep the boat upright is under athwart seats. This is a common practice on many small utility type boats.