Where ever you put it, do a trial mount first. Make sure you can see the key or dial or keypad clearly, and that the safe will open once bolted in.
We carry a small safe as well to store extra cash and passports and other stuff with us. I had the perfect location for it, but I started out by putting it in this "perfect" place and discovered that I couldn't access the key slot to open it and then discovered that even if I could turn the key, I wouldn't be able to open it wide enough to put anything in or get anything out!:S
Now on plan D, I think it is. Still not bolted in, just keeps moving around.:?