Snik,
wow, that's much more elaborate & large than I was expecting!
Which seat were you using it from?
Can you post a pic of it in your car?
Thanks for what you've already posted - those really help.
As you state, it seems way too big for a car, but could be great in a van.
You've mentioned you've done a lot of van camping&travelling, so you already have the experience & comfort-zone with vans.
For now, have you tried simpler options?
I've mentioned the $1 mixing bowl from DollarTree. It's the size of a bedpan, has a pouring spout, handle, and base. I had tried various cups, and all were
too small & too
stressful for me, for the reasons Doug stated so well.
It's not perfect, just another option to consider.
Does Suanne's blog have any helpful toilet details?
For car dwelling, that's my favorite resource:
http://suanneonline.blogspot.com/
I think everybody should give car dwelling a try, mostly so they
really appreciate vans and bigger vehicles.
P.S. David tried & meant well, so thanks!