It depends on what kind of wood. Cedar, Engleman,Sitka,Euro Spruce, Adi, in that order of stiffness.
I have Carpathian Spruce top thinned to about 1.08 with adi braces. (Shoudl have gone to 1.12) I have to redo some finger braces. This is for a 15.8 lower bout, 25.4 steel string. I may use light strings on it, but to my hands, it felt stiff, I just did little bit off the lower bout brace. I probably wont sand much off the lower bout, its pretty thin for a first build.
I have also notice (I think) that the Sitka brace stock that I had was actually stiffer, but a bit heavier than the Adi brace stock, and darker in color. So the stuff out there can really vary on stiffness. The Englman I had you could feel the difference.
I am going to set up a brace stiffness gauge soon, for the next guitar.
YOu should be going by a book or by plans, and both are usually 'overbuilt' to some degree.