Hi there
I would go for the fiberglass setting and also select low pressure piercing and brittle. A pull to open setup would also help you out. If you do start to have issues then try reducing the event and relay timings. I would start by reducing the figure in. The high pressure collom, time to clear abrasive from nozzle when finished cutting. By reducing this it would allow more abrasive to stay in the line. This will help when piercing.
Cheers