Kripps - What kind of glue are you using to bond the sintra? I think there is special glue that fuses the plastic together but I haven't found that yet.
Also did you use WOF's inner template or the layer the outer. I wasn't sure why there was a specific layer for the inner layer, when only the back is seen. It looks like this inner layer would get in the way of the cheek pieces that curve into the helmet, maybe not. I need to get started on this - I'll probably answer my own questions.