I deal with a lot of people who may or may not be stupid, but more of them are trying to do things they have no idea how to do.

So it helps to make sure where we are in a discussion before we go into it.

For custom coils, Espo Springs and Things are pretty good about making springs to spec and will work with you to figure out the specs.

http://www.springsnthings.com/index.htm

Airbags, dunno, I don't do airbags.

They say there are no such thing as a stupid question.
They say there is always the exception that proves the rule.
Don't be the exception.