Hi Larry,
The EtherRain controllers do not really generate much heat, they operate at about 0.5 Watt (yes, 1/2 Watt) each. Your network switch will generate some heat though. It looks like the cabinet has vents, but I wonder about how hot it will get within the wall cavity. Most networking gear is designed for open air operation.
Question, is the wall into which the panel is going to be placed an exterior wall that is subject to heat from the sun? If so I would think you might want to make the vents bigger. You'd want the high temperature to average around 80 to 90 F max with possible peaks to 100 F during the summer including heat generated from the switch.
Hope this helps,
Jim