It will be the same on either boat.

Your weight does not matter here... you are sailing a 2 man boat singlhanded. So.. you take the L4 correction.

Its not a penalty... it is a correction for your choosing to sail without a crew. Obviously, the boat is faster with just you on it... (providing you are able to keep the pointy end up). Since the boat is faster.. your rating has to get faster... so the rating number gets smaller.

Think of it this way... If you had a stiff boat with excellent sails and you sailed the perfect race.... you would sail the boat to its rating.... In the race against your buddy who is also singlhanded on the same kind of boat...in the case where you beat him across the line... he did not sail to his rating.... Several reasons could be the reason. he screwed up... he does not sails as well as you or his sails and boat were not up to speed. Now, when you race against a 16 sailing with two people. The handicaps are used to figure out who sailed better. The team sailing closer to their rating will win.