lower pressure is not better than higher pressure. lower pressure causes more heat buildup and possible eventual failure of the rubber (think firestone and the ford explorer incidents), also worse handling, braking, and gas mileage. the only time lower pressure is good is for off roading or snow. but even then all you're doing is getting driving traction, not braking or handling.
40 psi is pretty high, and you would eventually notice extra wear in the middle of your tire (assuming it stays constantly overinflated)
and don't worry about the fronts looking a little low, as long as your gauge consistantly says 34 psi you're good. radials will naturally have a little bulge at the sidewall, and that's where all the weight is anyway