@philipma1957 What are the operating temps at your 4 card rigs? Aren't they too close ? I know that stock rx 470-480 can get pretty hot when mining ETH. How did you solve that problem?
all are 60-73c
most of the issues of heat are solved due to no overclocks setting wattman to -20 to -32 power and the fans to high limits like 3000-5000 the temps to 65c - 73c.
plus all are open air rigs.
Also the front card runs coolest the back card second coolest the two center warmest.
that is true with the two reference rx 480 builds. finally
no card has a back platethe last build is rx 470's it has staggered msi 2 fan cards and 1 fan sapphire cards. the msi do not have back plates the sapphires do
it is critical to not do 4 cards with back plates.I don't dual mine . I don't over clock . I lower power limits .