cameras out of foamcore work great !
you can glue a sheet of plywood to the base
to mount your tripod.
you might consider a holder of some sort
to put your paper into ( or film ) so you can expose
more than one sheet each outing ...
i made a few book style paper holders that work great.
i've made them for 2x2/4x5/5x7 as well as 11x14 cameras ...
a sleeve to stick your arm into, and an exposed / unexposed folder inside the camera
works well too ... ( but takes more effort to make )

have fun !