Sorry, guys, but go back and talk to your old piano teacher (you know, the one with the ruler!) about correct posture while playing. Remember what she told you?
Seat hight, just SO...
Piano height, just so... (no adjustment there, anyway!)
Distance from the piano, just so...
These distances weren't coming off the top of her head to torture you. There a recognized 'best' position to sit and play a keyboard, that allows the easiest, freest range of motion for your arms, hands, and fingers. Now imagine the look of horror on her face as you tell her you want to prop up the back of the piano to angle the keys downwards..!
It's all about the angle of your wrist to your arm. There is a natural, unforced one when sitting at a piano, on a bench at the right hight (and, other than children and the very tall or short, that doesn't change much, to the point that most piano stools don't even HAVE a height adjustment). The only reason you tilt a keyboard up or down on a stand should be to preserve that arm/wrist angle for keyboards that are much higher or lower than standard height.
But angling the whole keyboard in a downwards direction, by several degrees, although it will help you to read the display better, certainly won't allow you to PLAY as well.
Or maybe your piano teacher was jiving you....