Just count how many connections you need.
Ex:
Each Joytick needs 4 inputs
How many buttons you need total.
According to your liking.
4 Player Joystick is 16 total inputs
a total 16 total buttons for player ( 4 each)
Player Starts need 4
Trigger for Coins 4
what else you need ?
The IPAC4 has 56 inputs so according to the MATH, you got it made.