Note that you have some reduced brightness if you matrix displays (HT16K33).
And a HT16K33 can't be used for big 7-segments with 4 LEDs in series.
What's wrong with the solution I gave you in post#2 (TPIC shift registers).
They use three Arduino pins for as many 7-segements as you need.
At full brightness.
You can find then on ebay for $0.50
Must use the common anode version of the big displays though.
Leo..