If I were to have a secret spot, it wouldn't be on the dash. It'd be hidden in my trunk liner(behind it). A spot where I would almost forget, a place that I would stumble upon a couple hundred bucks upon stripping my car while track prepping. lol
Luckily I don't keep anything extremely valuable in the car. If its worth is >$300(street price i.g. craigslist) then its going with me.