IMO 5% is excessive and I like to be able to see out my windows at night and I have 20% all around and it works for me. I do recommend doing 15% on the sunroof since that will allow you to have the shade pulled back for light but really cuts the heat to near zero.
'12 Focus Red Candy SE Sport 5 spd
'99 Toyota 4Runner Sport
'11 Subaru WRX STI Hatch