Depending on the amount of twist in the body, it can and will induce some stress into the frame no matter how many places it is supported, "IF" those locations aren't anchored to maintain a set elevation.

How much "perfection" are you chasing? Personally - If chasing to that level, I'd mount the chassis in 4 points minimum, close to the body mounting locations, and anchor the chassis as secure as possible. whether that anchor be the floor of the shop or a frame jig. A laser level can be used to verify "flatness" of the chassis probably down to a 32nd of an inch.