I am curious how this unit ran for you so far? It is built quite similar in design to the GQF models I have. I have only the two fans on my incubator and on the hatcher and I find that they actually produce too much air flow, drying everything too much in the process. I have run them with only one fan the last two season and find that it worked much better. With 4 fans in yours, did you run into that problem at all?
I also have used that same thermostat from IW, and it worked very well, but only lasted one season for me before I needed to replace it on my Leahy 624. Of course, that was constant running for about 5-6 months, so that probably makes a difference. I have concluded that it is wise to have stuff like that on hand for when they do die.