MOTM

I am designing a larger power jumper pc board with:

2ea 3-position screw terminal blocks (INcoming and OUTgoing)
some number of MTA-156 connectors

So the question is, how many MTAs? 16? 20? These are for "big ass cases". I
am
thinking maybe 18 is a good number.

You can always add another one in the case. That's the reason for the
OUTgoing terminal. You
use 3 wires and connect to the second pcb's INcoming terminal.

Paul S.