CAN-BUS Shield V2.0 issue using digital pins 23-53 on Mega 2560

I have a CAN-BUS Shield V2.0 connected to an Arduino Mega 2560.
Everything works fine until I start plugging switches into digital pins 23-53.
Then the CANBUS is not able to initialize.

Why would these pins affect the CANBUS?

Ok, figured it out.

Looks like Mega uses pins 50-53 for SPI.