Hi All,  A very common and inexpensive way of tilting the top of
a piano bench was to install two "risers" on the inside sides of the
bench, opposite the hinges. I have a diagram with measurements of
the most common variety at:

http://www.player-care.com/gifs/stolprop.gif

Other images showing where to place the risers are located at:

http://www.player-care.com/gifs/stolpro1.gif
http://www.player-care.com/gifs/stolpro2.gif

Musically,

John A Tuttle