105 litres is more than confortable for your 65kg.
This means that it is the shape of the Hobie that is the problem for you: too narrow, not enough width in the section in front of your feet, rails too thin at midsection?...
Try to go wider, especially in the area between your heels in paddling stance and 2 feet forward of them, not floatier.
For instance, in the Gong line, the board on the right is MUCH stabler than the left one, at similar width & volume...