ARGH, I know that.

Escept for grounding on non-painted metal. I did read that it should be on non-painted metal, but just assumed it grounded 'easier' or something.
I'll state my challenge exactly.
Everywhere says: Do NOT attach the final negative to the negative terminal of the dead battery. Instead, use a part of the engine away from moving parts, fuel lines, etc. Just stick it on part of the engine.
Now, I had to write a procedural document (legally binding) for work, about using a Jump Pack, and jumper leads. When I put to my boss that everywhere was saying "Do NOT" he was saying that's what he's done, and I was saying that's what everyone I know does.
Now, the challenge lies here. If I put something where I have read "DO NOT", as "you can" or "may", and something occurs, well... I don't really care that that's how my boss has always done it, and that's how everyone I know does it. All the written evidence, including Owner's Manual, says "Do NOT".
My boss wants me to put "Do".
I'm asking how likely, or has anyone heard of, or known someone, or experienced, or XYZ, a spark around the battery caused by doing what the evidence says Do NOT (but most people do anyway,) or had an explosion from the battery of this.
As said, I'm putting it in a legal document, and considering the evidence (no documented evidence, but just advice from experts who know more than I do in this field) says "Do NOT", but my boss says "Do", I have reservations. If there's a 0.00000001% chance, and it happens, that'll be a company document with my name on it.
[Obviously, I'm not going to say "Do" with this, but I've never heard of it happening, so I'm wondering if anyone has. Especially from kestegsssss who work with electricity and know more than I do. Although he's not an autoelectrician, but he's close enough.
Edit: Syxallis - with [youtube] tags, (the Music/Listening thread,) you only need the random letters code. So it would be [noparse][youtube]h3S7w2H3YeE[/youtube][/noparse]