Bit of red bit of blue -sitting on the fence then!!
You seem to have made you mind up mate so carry on.
The blue was not my text - it was an extract from one of the posted replies, I hadn't worked out how to quote just a section of a posting without including the whole thing - I'm still not sure I have but I'm giving it a try (my preview tells me I've got it sussed now). So the blue was to distinguish from my own text. The Red was to highlight that bit of text as I can't see a way to make some text bold.
Anyway, it's not really true that I've already made up my mind - as I said at the end, I want to know if my reasoning is wrong, and I couldn't see anything amongst the replies up to now that said I was wrong for any technical reasons - only ones that highlighted the risk of not complying with manufacturer's instructions, which, despite what ericmark said, a) don't clearly state that it is wrong (apart from the licensed specialist element) and b) I suspect of being over-engineered. Some of the responses appear to be agreeing that it is just over-engineering. But as I said, if somebody knows why this is not over-engineering, I'd be very keen to know that, so that I can avoid a big mistake. Does your "go-ahead mate" mean that you wash your hands of it or that you feel my reasoning is correct? I don't just want to be told "yes you're right" but nor do I want to be told "no you're wrong" without some decent reason.