When it comes to TVs we usually suggest going with the largest screen that will fit your space and budget. For projector screens, space is the main limiting factor.
Your drop down screen should be mounted a few feet above the floor to allow for a natural viewing angle free from furniture obstructions. Ideally, you’d leave at least a foot of space between the top of the screen and your ceiling so you don’t have to crane your neck to see. In a room with an eight-foot ceiling, a 98” screen would leave around a three-foot margin at the bottom with a one-foot margin at the top.
But, even when you have a lot of space, bigger isn't always better. Projecting too large an image can produce a picture with less than optimum brightness, or noticeable pixel structure.
The suggest distance for VIVIDSTROM Floor Screen: