Thanks guys for reply and yours ideas
I was surprised that board has none stringer that is at least strange.
For s fun I will try to put two marine plywood stringers with epoxy in 70% of length of a board, strengthen upper skin with fibreglass at least 3 layers and make stronger lower attachment surface of board making it wider and longer towards front of a board.
Maybe will work
That will be short time fix.
I am still in thinking to build new board at to try to make mount to some old surf board I have.
Does anyone has any details how to make attachment point to standard surfboard and how to strengthen it? Any info is appreciated.
By the end of a day when I have enough info will be building new board.