I sometimes run serial data ( shift out ) through all the displays on my projects ( TPIC6B595 shift register latches on each 7 seg display ) in a daisy chain fashion.
I know shift out is slower then SPI but I have quite a bit of capacitance on the ribbon cable I am running, and it works fine.
If there are only a couple of displays I send the LED supply through the ribbon cable too with minimum voltage drop. Otherwise I have separate power lines.
I am making a board now with 5 individual display " tiles " one with 4 numbers, and four with three numbers.
Instead of a daisy chain, I am thinking of running a single ribbon cable to each tile from the controller, with the clock, dimming ( notG), and data lines common, but each spur having its own latch pin from the 328 chip ( I have plenty of spare pins )
This way I just need 5 (14 way) ribbon cables to the tiles. ( 5 of the IDC connector are ground, and 4 are the 12 volt LED supply. )
Does anybody see any hassles with this ? all the chips will have the same data shifted through them, but only the spur with its latch low will store the data to show when the latch is taken high again.