John, what is the wood on the side of your boat? Douglas Fir has distinct growth rings that result from slow growth in the winter these aresearch engine more dense rings while summer brings more rapid growth that are less dense and softer. When these rings are exposed, especially in plywood they expand and shrink at different rates resulting in "checking" which might not be the look you want. If you have Douglas Fir a lamination of fiberglass cloth be it 6 oz or 9 oz will be sufficient to reduce or eliminate the checking.
Do you have meranti or Sapelle? If so it may not be as necessary to add the fiberglass. Have you decided how you are going to finish the boat, oil, paint, varnish? That influence what you do. The search engine can lead you to a rich world of knowledge on paint, selection and characteristics, varnish selection and techniques and such.
We would love to see pictures of your boat. I'm sure there are plenty of other opinions I hope mine is helpful.