This will be no use to you now but may be useful next time.
If I have to drive a car in any state other than road-legal, I type up a letter of intent. In the letter, I write where I've come from, where I'll be going, and why. Where possible I include times and routes. I sign the letter in blue ink and date it.
This letter has helped me on two occasions. It helps establish in the mind of the officer that my trip is pre-meditated and for an appropriate purpose.