Behind the base cabinet door in the bathroom, there was an opening with water supply lines blocking use of the space. As well, the wheel well was a different height at the rear. So I relocated the piping, raised the floor and put sidewall pieces in. This space was also the access point to the water pump (beside the toilet). Dumb arrangement so I removed the fixed panel there and put in a removeable panel.
Now there's enough space to store over 24 rolls of TP.
The last thing to do in the bathroom is figure where to put the danged TP roll holder. Still scratching our heads....