I have the wire a little more slack than I would if I were cutting something like wing cores. This causes the wire to bend away from the advancing foam and builds up tension in the wire which actually helps achieve a smoother cut. The tension helps by pulling the wire through the foam if and when I pause while pushing. I use this bend in the wire to also judge my cutting speed. If I slow down the wire straightens out. If I push to fast the wire starts to bend more. If the bend stays consistent then so is my speed.