A half inch? Should only be enough for the tank to clear the uth.

You will have to find what temp you need the tstat set. First off the substrate should be no more than a 1/4 inch over the uth. You lose some heat but with thin glass and thin substrate layer it shouldn't be much higher than your desired temp but it may be by a few degrees. Take it slow and allow the uth to level out before changing the tstat again if needed. They don't change that fast so like I said take it slow.