I am going to check with my policy documents tomorrow. I suspect it comes under "any modifications" which at least here in the UK you have to declare. I don't think there it's an area for interpretation it either complies or it doesn't. If it came to it you could of course take them to court arguing it wasn't significant but they would fight that extremely hard, it would cost a fortune in legal fees.

I don't think the Ford/Firestone case is relevant. It was nothing to do with the policy holder being at fault, this would be.