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).
The 16 is only faster singlehanded in a very narrow range of conditions (i.e. up to maybe 8-10 knots). You just need 120-130 kg to get it going in anything over 10 knots. I would go for a 18 with wings, so you can get your weight way out.
