All you need are two mirrors, taped together with duct tape.
Then stand them on end, like a book, standing up.
Open them to 90° and you can get a preview of how a 4PP would be.
Close it a little tighter til you six pies ... and you get an idea of OBW.
Close a little tighter for 8 pies ... and a preview of SAW.
Move it around on the fabric, so you can see the different looks you'll get.
I found "locker mirrors", framed up in plastic for all of a dollar each at the $ $tore.
I keep them in my truck, ready, just in case I find some fabric I think I might use for this.