that looks to me like the pdf download plan. As far as the tunnel is concerned, i would if i was you keep the width and length the same ratio as the plan suggests, by all means make the boat bigger if you wish but keep the ratios the same. These boats are designed very precisely with lots of maths involved. if the tunnel is too big it will create too much lift and flip your boat.
one of the reasons why this boat is not a good starter is because the framework has to be
dead square. During drying the frame work has a tendency to warp and twist so as the vaka's (if this is the correct word) are no longer parallel. Even more so when the outer skin is put on. You will have to come up with a method to prevent this warping during drying because if 1 vaka is higher than the other it will be in contact with more water causing unbalanced drag which at slow speeds will cause the cat to corner and on plane could be disastrous.
for the frame i would use 1/4 inch balsa or 3mm ply and for the sides 1.5mm ply. But this is my preference other people will dispute this no doubt but unladen this hull could be under 800 grams. keep us posted with your build and good luck!!
