ursblank said..
By "cork effect" you mean the board is moving more due to lack of inertia, right? 130l vs 74kg gives a ratio of 1.76.
No it is being too high on the water, on a too narrow board, kind of standing on a barrel. And the chop will have more leverage on the board to move it.
Volume helps widening the sweet spot, especially fore/aft: that is the zone where you can move your feet without the board sinking tail or nose.
I would go wider, especially since you are tall (well taller than me). Geometrically, you at 186cm on a 30" wide board would be like me at 167cm on a 27" board.
Wider in the tail will also help balance, especially when resting on your heels, and be more adapted to small/medium waves. You do not need to get too much down in volume, I would stay above 110 liters though.
Heavy boards are stabler, but the difference is much less noticeable than width. And light boards are much more pleasant in smaller waves.