@A340Yumyum, he does ask a perfectly reasonable question and if you don't want to answer it, don't waste your time replying back to him, you only put off our fellow colleagues within the industry from asking for advise. The answer to that question is not definitively answered within this forum. However, even if it was, I don't see that reading through 157 pages of Pprune is doing your homework and taking 'goodness knows who wrote that article' as gospel.