I used to work for a place that built fast cars. We had a mate that used 5.0 or more for the factor of safety everywhere. Everything he designed was about 30% heavier than it needed to be, but we could easily adapt his parts for prototyping because it never mattered if you drilled a hole through the middle or cut them in half. They were plenty strong and reliable.

We called this the “Factor of Lloyd” and we had a few sayings about it.