Forgive me for not reading through the entire 15 pages of this topic. ( I am new here).
My take on this is this:
My Volkswagen golf sportwagen had a slide out bin under the driver seat ( this is where the gun nuts kept their handguns). Good storage space under the center armrest. The armrest pivoted up. slid forward /lock in position for comfort. Had a sunglass holder in the roof /headliner. All doors had plenty storage for umbrella, waterbottles and so on.
After I removed all the stuff from the VW ( including stuff from the trunk -spare tire area- was deep) and all was in boxes, ready to transfer to HR-V. I ran out of room on the HR-V.
This included jumper cable, mini air compressor/roadside kit., tire plug kit, first aid box, flashlight, few simple hand tools -screw driver, adjustable wrench, pair of pliers to pull nails out of tire if needed. Umbrellas (2), rain poncho... and so on...
Being an ex mechanic, I want to be able to rebuild the car on the side of the road if I need to. (kidding)
In the end, I had lots of stuff in the box I ended up not transferring to the HR-V because of lack of space.
This is a good thing, most of the stuff I never used.
But if I fall off the bandwagon and go back to bringing the kitchen sink with me, the rear seats have plenty storage under it.
The HR-V forced me to reduce being a packrat and be a better man