Particle board works just fine. The only disadvantage is it is quite heavy. using 3/4" instead of 1/2" is also OK, but will weight even more. The Guillemot Double forms are quite heavy to begin with and 3/4" particle board will make them particularly so. If you can find help when it comes time to flip over the boat, the weight is not a big deal.

: Hi! I am totally new to this. I am just gearing up to build my own Guillemot
: Double Kayak. Still in the process of reading and getting my tools ready.
: Has anyone used particle board for the forms and if so how did it work? I
: have some 3/4 in. particle board I would like to use if it is workable.
: Would anyone care to respond. It would be very much appreciated. Jacques