Here is my advice. Elderly has good plans for a concert size uke that include a pineapple shape. Get them. For a first instrument I would use a standard concert scale, changing the scale length increases the string tension adding variables that you are not ready to deal with. At this stage it is best for you to follow the design perfectly. After you have built a number of instruments is the time to start experimenting. As for wood, get anything that is readily available, reasonably priced and appeals to you. I would definately use mahogany for the neck. Do not use rare expensive, lutherie grade wood for a first instrument. You will make mistakes with this instrument. As your skills improve, then more expensive and exotic woods can be used. Good luck with this and let us see the results.
Brad
