I’ve seen a few good ideas on TM suggesting improvements for storage locations. After fiddling around for a while to get some additional storage before going on the Laon trip last month I came up with the following – so in case they are of use to anyone else, ideas for the options pot -:
Under spare wheel storage:
First I put a wooden support along the base of the void below the spare wheel and over the plastic (on my car) trim for the fog/reversing lights. The wood sits on the lip of a chassis cross bar so any weight is mainly on the chassis not the plastic trim.

Finding some suitable containers to fit was more of a problem but I came up with some 1.9 litre containers with clip on lids. These proved to be quite a good size and shape to take bulbs, tools (spanners, scredrivers etc), and other odds and ends.

Better still, two fit neatly lengthways across the width and another two stack on top.

There is little lateral movement and they are prevented from bouncing around by the spare wheel and a suitable piece of neoprene under the bottom of the wheel. This allows four of these containers to be stored in the void under the spare wheel.
These are now used for stuff that is not routinely required but nice to have on a trip.

Rear luggage rack:
There are many ideas of luggage and modifications to the high level (cobra – type) brake light to accommodate suitcases waterproof bags etc. Using the idea of containers I came up with an alternative of two 9 litre containers and a 4 litre container. Arranged as shown they provide easily accessible rainproof (and cheap) storage while allowing reasonable visibility of the high level brake light (but not 180 deg visibility) with no mods.

Alternatively, only two 9 litre containers could be used arranged lengthways across the luggage rack so total (180 deg) visibility of the high level brakelight is possible – but on my luggage rack this option does require a piece of wood to prevent the containers slipping down the gap between the luggage rack bars.

We used these for shoes and washbags etc leaving much more room for clothes in bags on the rear shelf.
The 9 litres boxes are also, strangely, just right for 5 bottles of wine…..