Here is a thread about the IQ test part of those MC4s in case you run into that. No second chances with the little internal grabbers. Can't pull it out again. The photos are gone with tinypic, sorry.
There are a number of different MC4s on panels where some are one piece and some do unscrew, so first see what is on your panels.
I thought my panel pigtails were cu-al, but after guys on here said to check, I scraped the strands and it was tinned cu. Hard to tell with the silky thin strands.
I used #8 cu onto the panel pigtails. Yes, Amazon, etc have much better pricing that I paid for my MC4s, but I only needed a few so no problem. Don't know about wire sourcing.
You have to start at page 1 after going here
https://www.rv.net/forum/index.cfm/fuseaction/thread/tid/29910358/gotomsg/29910840.cfm#29910840
