There is more to "Category" certification than twists. If the larger gauge cable s not "Category" certified, you have no way to know what the performance will be. Chances are it'll be worse than the Cat5. You may or may not get traffic through the fat stuff, and unless it has a good crosstalk spec, it's going to suck. Bigtime. Also, have fun finding termination for that stuff ...
But hey! if you're into wasting time & money, have at it.