Originally Posted by vagpwner
ive decided to go with a conventional design but how should i know what
angle i have to place the prisms at to get the proper image?
There is no actual fast rule for this as the exact angle for the prism rotation is based on the angles of the prism themselves and the throw ratio of the set up. Example, if you set up a lens using prisms for a short throw, the decide to increase the throw ratio, you will need further rotation for the longer longer throw. This happens mainly because of grid distortion.
The best you can do is to make a 2.37:1 screen, then project your 16:9 image (top to bottom is framed, left to right is centered), then add the prisms and rotate until you get the edges aligned.