Where are you located? Some one may know of a place nearby where you can obtain the necessary plywood.

You might want to make "material availability" one of the top concerns when looking for a design to build.

Many S&G kayak designs do not require the plywood to be twisted or deformed very much. For these you could probably use the nominal 1/4 inch lauan without any problems. Multichine designs, by virtue of their many pieces, don't usually need to twist individual parts very much. On the other hand, there are a lot of hard chine designs which have very flat sides. The plywood bends easily into shape for these.

However, I would avoid using such materials on any design which uses the term "tortured plywood". Using lauan with such designs could prove to be a real torture for you.

PGJ