I once saw on another website (I believe it was Marcos Magnum PI Page - now down because of some German copyright issues) a photo of the actual surfski used in the series. It was sitting in some warehouse that had a bunch of Magnum PI and Hawaii Five O stuff stored in it. It was kinda sad really.
That was the old studio used for H5-0 and MPI. I saw photo of the surf ski hanging there as well. Kind of sad when you think about it. I always thought it would be a great usable piece of memorabilia. I think you have to buy a surf ski according to your measurements, and since TS and I are the same height, I always thought it would fit me.