Great question! This is the toilet I have: https://www.amazon.ca/Dometic-301097202-Portable-Toilet-Gallon/dp/B002A3E3HQ?th=1&psc=1&source=googleshopping&locale=en-CA&tag=googcana-20&ref=pd_sl_8d8uz2vfi3_e
There is a “trunk” sort of space in the back of the van that I am hoping to build something to house the toilet, so it’s not just sitting out in the open. I’ve seen a few different ways of doing it and one of them is like the one you describe. But since it will be in the trunk area, I don’t need it for seating -but I want to find a way to use the space above the toilet for storage or something. Will keep you posted on what I end up doing!