Size matters.

I have a few of these boards

https://www.ebay.com/itm/124217882169?

and lots of bitmain psus

if I alternate

 slot 1 big msi 5600
 slot 3 big msi 5600
 slot 5 big msi 5600
 slot 7 big msi 5600
 slot 8 short power color 5600

5 x 40 = 200 mhs  no overheating as the last card is short and will allow air to get to the slot 7 msi

this is a 200 mhs unit for about

 1300 usd in gpus six months to pay

psu    =    free I have it.
cpu    =    free I have it
ram   =    free I have it
mobo =   free I have it