otherwise you make find the smoke escaping from a small wire not designed to carry that volume of smoke....

Got me worried at first...

(Yes - I did replace the small wire afterwards!)

Usually melts the accelerator cable or choke cable if you're unlucky.

Mounted my horn on what I thought to be a piece of non conductive fibreglass, cut from my dashboard blank (carbon fibre surface). (Sierra item needing switched earth)

The smoke which ensued as the carbon weave warmed up and burned the fibreglass was a bit of a worry, though it didn't even warm the feed wire.

Luego - I can confirm that your dashboard is carbon fibre faced, and not just "look"