Just wanted to thank everyone for the help, this is what the rig looks like. 8.5 GH/s

I'm loving that!

You're also beating my 8-chip setup which seems to peak at 9GH/s and then rapidly dip to ~3 on chainminer. For some reason, I get 4,5 or 7 chips detected, depending on the direction the wind's blowing
If I thought I could get my hands on some more chips, I'd be tempted to respin my board with a way to take dodgy chips out of the SPI chain...
Did anyone ever get a QFN ZIF-socket and build a chip tester?
Guys, is a level converter essential or is it optional when connecting to a rPI? Thanks