Are Four 74HC595 Sift-registers in a row too many?

[runaway_pancake]

This display ?
http://www.youtu.be/OW8FVmrA7js
has 9 '595s daisy-chained.
The display has 70 pixels, the 595s have 72 outputs total, so I have to knock out two dummy bits at the end to push everything through.