You've answered your own question in many ways and there are other things to consider.One thing to remember is to make the sinew work to it's ability in a design on a good piece of wood.More where needed in the working portions of the bow limb.Less where not needed in less working stiffer portions like the tips.That means putting the bow in enough reflex also to make it work for it's placement too.
Putting sinew on a flat profile bow without changing it's profile will not improve performance if that is what you are asking and will serve no more purpose than protecting the back and raising the draw weight and in all probability actually slow the bows' performance down.
