You can't use tear away on cotton for dense designs as cotton is stretch and you will get puckers. you can use a poly mesh for the cutaway and float a soft tear away underneath depending on the density of the design if it is really dense you will need to use a medium cutaway and float the tearaway underneath. also if you are doing embroidery over piecing lines make sure you use a poly thread to piece with because embroidery can pop cotton stitching out. Embroidery will generally make the area stiffer regardless of the stabilizer chosen due to the thread density, unless you are doing a redwork like design or designs with minimal satin stitching. Dense designs are stiff most due to the thread in one area.