I've installed the axel fan today, along with a programmable thermostatic controller. I've positioned it above the non-watkins motor, fastening it to the exhaust tubing that used to connect to the back end of the watkins self-exhausting motor. Now it's pulling cooler air into the equipment area and exhausting it to a vent on the side of the spa. There was direct sunlight hitting the equipment compartment cover and initially the inside temp was 105ª with the spa off! I've programmed the fan to turn on at 105 and off at 98. I'm shooting in the dark with pinpointing optimal temperature ranges, but I did want to see how fast the fan would work to cool down the compartment. Having said that, we don't use the spa in the heat of the day, so in actual use the outdoor temps would be cooler, as opposed to daytime when the ambient temp was 79 or so (direct sunlight played a factor today). As I write this, I've gotten the rig up and running for about about 2 hours and the fan has cooled the cabinet down by about 6 degrees.
That's why I was trying to pin down the operating temperature range of the IQ2020 circuit board, if for nothing else to gauge how to set the operating parameters of the fan. (it's a 3.5" 110v with a high CFM). I'll be playing around with this for a couple more days, but so far it looks promising. The vents are also a good idea. I'll update this post as I learn more.