I am working on a GFG also. I have done about 93 flowers. I think I totally understand what you are saying. I think you are only using one cardstock(that is my preference too) but at the corners the fabric is now folded to where there is 4 layers. I just basted one to see how exactly I am doing it. In my corners where you are talking about I have three layers. Depending on the fabric, it usually goes through pretty easily. Some fabrics require a little help. I am wondering if your cardstock may be too thick. I am using a package from thePaper Studio which has 50 sheets of 8x11". It doesn't have a weight on it but check yours to make sure it is just cardstock and not something heavier. And the corners should have only three layers of fabric. Good luck.