Roll Bar angle

Does an 8pt roll bars main hoop need to be on a certain angle of recline or decline? I want to install mine next weekend but S&W didn't say anything about any certain angle for the main hoop. I was planning on alligning it just behing the door jam within 6in of me when seated etc. I noticed at a few car shows that some have a noticeable recline of the main hoop while others are straight up and down 90 degrees to the floor. I can't find a good trustworthy source online so if anyone knows a good site please let me know. ThanX,
Adam