Ignoring the weight of the mast and effects of waves and wind, a float at the head of the mast would need to displace 91 lbs of water in order to support the weight of the high hull. At halfway up the mast, with the additional heal, you would need 368 lbs of displacement, again negating effects of the mast weight, waves, or wind. All of this is without any safety factor and a rather dirty calculation.