I played OVER 3190.5 for a big bet in May when I posted on twitter. I project him for around 3700, so yes I still would lean over at 3500.
For Murray to go under 3500, he would have to throw for under 218 YPG. With the Arizona play volume, pass heavy playcalling, and likelihood to be playing from behind... that number is not going to be hard to attain. 29 QB'S last year threw for over 200 YPG!
I am not saying Murray will be a franchise QB... but I do believe 3700 pass yards or so is what his expectation should be.