The semolina I have on hand came from the bulk bin at Whole Foods so I have no idea what degree of coarseness it is. Since I have also seen the Bob's Red Mill brand sold at Whole Foods, I called their 800 number to see what their semolina is. I was told that it is coarse, not fine.
I used my semolina recently in a dough and I couldn't detect any "grittiness" in the finished crust whatsoever. I would just try what you have and see what happens.