Use the Underweight Modifications in the Portsmouth Tables. Take the base (D-PN) or wind adjusted handicap and multiply by the modification factor to get the modified handicap. Note that there are different modification factors based on just how far underweight you are.
Portsmouth Tables The modification factors are in Multihull Mods. D-PN should typically only be used for distance races. The wind adjusted handicap should be used for bouys races.
It is possible to sail solo H16 class legal but you have to be a big guy. HCA rules limit the amount of adjustment weight to 50 lbs. Therefore, if you are 235 lb. or more, it can be done.
