you should keep in mind that if its  not lycra it is not stretchy at all.  broadcloth cotton is very stretchy by comparison.  there are top line patterns that recommends either cotton or silk or wool.  that garment is cut larger.  so if you want to substitute a well fitting cotton pattern on your own accord, you ahve to use a larger pattern for slk.  remember silk grain of stretchiest is the other way around so the base of your top or skirt or pant should be parallel with the selvage. something like that.  I learned all this buy fabric substiting project.  i wanted to make a small cami like muscle top and utilize all variations of fibers without the blend....  using a cotton recommended fabric and the silk fit like an armor it got so small although I could put it on, there is no drop so the top arm holds and stuff fitted on me like a dressform.