Planning to build my first kayak soon, and wondering about what to use for forms and a strongback. I can buy 4x8 sheets of 3/4" MDF for $20 locally, and was wondering if this is a reasonable material to use for forms. It seems everyone talks about using 1/2" plywood? Form cost seems small compared to everything else involved, so I guess a few dollars either way for a better material isn't going to break the project. What thoughts can you share on the ideal form material? MDF vs MDO vs particle board? 3/4" vs 1/2"? I especially like the flatness of MDF, and the ease that it takes pencil marks. Conversely, I've always disliked the waviness of plywood. I haven't decided on staples/brads vs none, if that makes a difference.

Thanks.

Mike.