Smaller 3x3 Storage Units

What about having slightly smaller 3x3 storage units for things like boot-strapping supplies?
I'd suggest using the same or slightly modified models of the current unit/loose/fluid buildings scaled to a 3x3 footprint and 80% height w/ single a input and output port on opposite sides similar to the current. As for capacity, suppose the walls of the current buildings take up 1/2 grid unit on each side, hence the current 5x5 buildings have a 4x4 interior: 16 storage "cells". Storing a total of 180 units, this gives a capacity of 11.25 per "cell". A 3x3 building would have a 2x2 interior, and if scaled by 80% height, its capacity would be 4 "cells" x 11.25 units/cell x 80% height = 36 unit capacity.

Or, it could be scaled to 60% height, same as the horizontal scaling, and limit the capacity to 20 units -- a single truckload.

Re the construction cost. A standard small 5x5 storage costs 30 construction parts. If we assume the storage is basically all in 1/2 grid unit width walls, as per my consideration for storage capacity above, a 5x5 storage unit (25 tiles) has a 4x4 interior (16 tiles), leaving 9 tiles worth of "walls" costing 30/9 = 3.33 construction parts per "wall" tile. a 3x3 storage unit (9 tiles) would have a 2x2 interior (4 tiles, as per above), leaving 5 tiles worth of "walls" for a base construction cost of 5 tiles x 3.33 parts/tile = 16.67 parts. Scaling by the 80% of the reduced height as used above would give a construction cost of 13.33 parts, so just use an inbetween value of 15 parts, which is incidentally half the cost of a standard 5x5 storage. (50% cost for 36/180 = 20% storage, there really are economies of scale!)

Incidentally, using these calculations, a full-height 2x2 storage unit would have 1 tile of interior for 11.25 units of storage, with 3 tiles of wall for a cost of 10 construction parts. That's less than a truckload, so of questionable value.

There was a mod that made smaller storage units. But it was not upgraded to work for Update 2.
https://github.com/tetrahedral/CoISmallStorage
There were 1x2, 2x2, and 3x3 storage units.