cross section diagram of an SLR+ mirror ideas to invert camera obscura image

from here

i need to think about how i am going to invert the image onto the hanging muslin effectively with minimal participant assistance required- i.e. i can set it up before i leave the shed for part two. possibly shed scientist/dorkbot/instructables approach of adapting an old SLR (diagram above for inversion of image) into some kind of projector attached to the wall? of simple box of 3 mirrors at these angles? how would this compare to angling a shaving or vanity mirror? try it!! a possible complication i see is in not using lenses in the construction to focus the light?