ruby2shoes

I have been teaching myself, with a bit of hand holding from the forums, to fpp and am fairly pleased with how I have managed my "practice blocks". I've signed up for a general class at a P&Q shop so I can have my work checked to make sure I am on the right track before I start cutting and sewing my "real" project. My printer will not accept any paper other than copy paper and I have noted that many people on the forums also use it so that's what I've been using. I've had no problems so far, have been using a 14 needle and a stitch length of 1.8 and have found it fine to machine sew through and the paper tears very easily. However the P&Q shop lady was a bit concerned when I told her, and advised that I should be using a finer paper and a smaller needle. Why? If this seems to be working for me why? And am I using the wrong size needle? I thought a 14 would cope better with the copy paper than a smaller needle but as I am intending to use batiks in my project, would the size 14 be too big to use on batiks? I can't afford to buy special paper, I can't afford to pay to use a printer from somewhere else to print out my foundations on the thinner paper, and I am hopeless at tracing by hand and if I have to do that I just won't do fpp.

So....is it ok to use copy paper like so many people seem to do? What size needle should I be using in my machine?