Throw a strap over the front; buttons in the back. And drive like it's not really tied down well (read... 'wisely and slowly'). It's like when you tow another vehicle with a strap; we all do it, and we drive differently because of the conditions.
Gravity wants to keep it in the bed. It's not going to slide forward in a panic stop. And if you don't accelerate like your at a drag strip, it'll probably still be there when you get there.
You're asking on the forum, but you already knew the answer. You just needed confirmation. Now you've got it :)
