in my own experience, if your line for the prussic is a bit smaller than the main line it will grab and hold much better. if you do use the same size, you will need to do more wraps and it will not hold as much weight w/o slipping because it cant grab the same as a smaller line would. I use mason line as a prussic on some small dacron line, it works fine, but i did try using dacron for both the prussic and RL and it wouldnt grab at all. Just try it out for yourself because there is no better knowlege of this stuff than to have your own experience with it. you can read all you want but things will be different in the field, so just dive into it and give it a whirl.