I have found that there are numerous cubby holes that are covered over for access panels.
• Under our sink shelves for accessing the plumbing.
• Beneath the bottom shelf of our pantry for accessing the tub.
• Beneath or bathroom sink, the linen closet, and under our refrigerator.
Obviously they were not intended to be accessed for storage but there is no reason why they cannot be, probably most handy for those seldom used items or storage.
You have to be a bit handy to do this.
Remember you are downsizing from a 5ver, so you can only cram in so much weight.