Thank you! Yes, regular M3 nuts and M3x6 BHCS for the backers. These would be nicer with a FHCS in there, as there is already a recess in them for that, but the kit didn't come with those and I don't have enough spares in my inventory either. So BHCS it is, still looks good enough for now.just regular nuts in the 1515 for your backers? nice build btw!
I may splurge at some point in the future and get anodized titanium screws to go in there, make them blue to match the printer primary color...