Not bad, but as you are learning I suggest you also go for the technical side and the interior design.
This way you learn a lot about what is crammed inside, which will also determine the external dimensions.
I bet if you set up a virtual build thread on your design you would get tons of input, though limit the size to either 15m-18m or a 24m-26m as that is what most on here might own one day.
On this size you also need to consider the usage of the available space more then on bigger yachts so you might learn more.
But hey that is just my opinion, and the forum is known for it's divercity so I might be corrected by the next poster.
There is a lot to be learned from threads by jfm, mapism, bartw and vas so you might to read some of those.