Recently in my overnight diaper testing have tried using the heavy duty hooded disposable tyvek jumpsuits.
you would not think they are the most comfortable to wear while sleeping but they have a thin cloth inner layer and the outer paper/plastic like layer will hold water (I tested this before using them) and still allow your body to breath a little. you will have some condensation if left for an extended time with a lot of moisture or body persperation but no leaks that I have found.
be sure to tuck the hood in the back of your suit or remove it if you use a hooded one to protect from suffication risk.
in my opinion this is a good option for overnight diaper testing when matress protection is not much of an option and protection is needed.
wondering if anyone else has ever tried this and what your experience was while trying it?