I have been working heavily on iterating the design of the flip display, I have removed nearly all the glued finger joints and replaced them with T-joints using M3 machine screws, nuts and shake-proof washers.
I have also removed the middle wall and replaced it with a small motor plate and M3 x 20mm spacers.
I have also figured out the correct dimensions for the top front lip to allow the characters to stay in the right place until they are pulled down out the way for the next flap.
Finally I have switched to a metal 5mm steel shaft with bearings on either end and MXL timing pulleys for the motor and the spindle.
The MXL timing belt connects the motor to the spindle without a middle wall to support any gears.
M3 x 20mm spacers hold a dramatically smaller motor plate in position, supporting the weight.
To square up the unit and keep it rigid a top and back panel have been added to the housing.
In the distance the pulley is secured to the metal shaft which is connected to the motor via a MXL timing belt. The pulley protrudes from the disc on the far end to reduce the width of the entire assembly.
In the middle a universal mounting hub is connected to the spindle. This buries the hub inside to further reduce the overall width of the spindle.
On both ends the shaft is held in situ by a small (5mm ID x 9mm OD x 3mm W) bearing that is secured with two M3 x 6mm screws and nuts.
The tension of the timing belt helps to prevent the spindle from sliding free and falling out.
No front housing is present but could easily be added.
This side plan view gives a better sense of way things are connected.