The Morningstar 45 PWM I installed has terminals that takes huge wire, perhaps up to #2 or #0.
When I ran the wiring from the panels, I ran a pair of #10 from each panel on the roof to a junction box next to the controller. From there, I installed a set of fuse holders on each + line, then connected the outputs from all fuse holders to a common binding strip. Likewise, I connected the negatives from each panel to another binding strip. I used 2 1' lengths of #4 from the binding strips to the Solar input terminals on the controller.
This made running the wire much easier and less costly, yet are more than sufficient for the current from each panel.