I assume that the flo mounting system that you went for is the flo modular?
According to the flo website:
Flo Modular can support a triple screen cockpit for 22” screens in landscape or 24” screens in a portrait configuration
Did you just ignore that and hope that it worked with 27"
I am now thinking of going for the same setup as you but as I currently have 2 20 inch 4:3 monitors I am worried about the space requirement for 2 27" monitors. There don't seem to be many smaller 4k monitors around...