Wow only 6 darks? That's awesome! Haha yes for me the city lights are NW so any widefield in that area looks like a sunset too. I love full frame DSLRs, there's just something about them... I wouldn't touch the IR filter either, probably better to get a modified Canon I guess. Judging from your pics I was motivated to do some multi-minute subs last night from a dark site. Hopefully they will turn out good
The file sizes are just absurd, especially if shooting and editing in Raw.
Looks like you'll have fun with this setup! Cheers