You claim to have sailed at 6.5k in apparent winds of 18k @ 28degrees. That equals an angle of about 43 degrees and 13k of True wind.
CONGRATULATIONS: That is the same as an 80 year old Full keel, heavy displacement, 36' William Atkin design.
What did you say your boat was?
Do yo mean that the hundred year old designed William Atkin's make 35º true wind
against 2.0m short waves?
Believe in what you want. I would take for an ignorant any person that think that the performance of an old designed full keeler that was not even a race boat in its days can be remotely compared with the performance of any modern performance cruising sailboat. If the boat is specially good upwind the deference will be huge in pointing ability.
Anyway I had said 27/28º. If we consider 27 (the boat was oscillating between 25 and 29 to pass the waves powerfully without losing speed) that is properly a more correct value you will have a true wind speed of 12.6K to a True wind angle of 40.6º. Even if the apparent angle was 28º it would give a true wind of 42º. I have sailed enough boats, including performance boats to know that is a very good performance given the sea condition. My boat is particularly good upwind, it is a modern performance cruiser with 2.25m of draft and Kevlar racing sails.
My previous boat, a 2002 Bavaria 36 was able to do over a plotted coursed course and angle of about 45 degrees (in normal Ocean conditions, not on the ones that I was talking about). I know for experience that the Bavaria 36 pointed better about 5º degrees of what an Oceanis 395 can do.
An Oceanis 395, the one with the deep draft, will outperform by many degrees an hundred years old Wilian Atkin's designed 36ft. My current boat outperform the Bavaria 36 (with long keel and premium sails) by about 8 to 5 degrees, much more in difficult conditions like the ones I was describing.
But of course, anyone is free to think what he wants. Look for a recent thread about pointing ability and plotted courses and you will come back to reality.