The One Ocean Kayak site has a calculator for working out how much timber you need.

http://oneoceankayaks.com/smallwin/stripcalc.htm

I am one of those builders who prefers short strips. It has worked well for me om all eleven of the kayaks I have built.

I use the belt sander method of creating the scarf as described in Nick's book. I glue the scarf together as I fit the strips onto the forms. I find that method quick, easy and accurate.

The sheer strip is the one exception. I think it is easier to be sure of a smooth curve with a full length strip.