Yes, window tint will cool down the interior by several degrees, unfortunately here in CA it is illegal to tint the drivers or front passenger windows. If you use limo tint on the rear window(and X-cab windows if you have them) and run 35-40%(allows in 60-65% light) on the drivers/front passenger windows, there is enough of a difference between the two tints that most LEO's don't seem to catch it/or care, but anything darker on the front windows, and you will likely get pulled over just for the tint.
51* at the vent is to warm if it had been running for a while. Did you run an oem r12 freon, or an oem system converted to r134?
