Lens Shift Question
So I'm having a bit of trouble wrapping my head around projector placement. I don't have a projector in mind since that's pretty far away, but since I'm trying to put the projector in the soffit in my HT build, I'm trying to get everything planned out before I put drywall up. If I can't put it in the soffit, then I need to plan projector placement hanging in the room somewhere.
My question is about lens shift. I'm using the Sony VPL-HW55ES for an example. In their manual they said you can have 71% vertical lens shift. What exactly does that mean? I can mount the projector up to 71% of the screen height above the center of the screen? or the top of the screen? I haven't ever set up a projector before so its a pretty noob question, I'm sure.
Basically, the screen size I'm looking at is 130" wide 2.39, 54" vertical. If I mount the projector 44" above the center of the screen (which puts it in the soffit, about 16" above the top of the screen), am I okay?
This also puts me at about a 17'-18' throw as well. Is this an acceptable throw for modern $3-5k projectors?