you have the fans already and can set it up for thermal operation so go for it. i'm sure you don't have to glue the sensor and besides voiding warranties the glue might not hold it, but i'm sure you can clip it on there somehow. i'm not personnaly experienced with how the gt looks to do this best and maybe sg could advise on that aspect after you describe the sensing device used to him. you will have to try and set a good temperature on the fans for best overall operation as you don't want it at 130 degrees, but too low and you might as well just run the fan without any thermal sensor and just time it with a timer.
as to saving power, yes that's good to do, but at what cost would you want to save 10-15w? that reminds me of a place i worked at that wanted to save money from the employees so bad they installed $3000 (circa 1980) time clocks to do it. they deducted the 1st 10 minutes of your time if 1 second late (up to that 10 minutes and the rest after that minute for minute) and do this 3 times and you're up on suspention so for about 100 employees allowed to do this up to 3 times a year at a $10/hr average it doesn't take much to figure out they wasted more of their money to save some money. btw, it didn't work any better than the previous time clock either.

Okay, I took your advise and installed a fan on a timer to see what the difference would be in the heat sink temperature.

AC timer = 5.00 (Home Depot)
40 Watt Fan= 10.00 (Home Depot) Smallest fan I could find.
Total cost is $15.00

I have the fan set on the low setting and it is drawing 29 watts. The fan is cooling both inverters. My heat sink temperatures are now running at 107 degrees instead of 130 degree.
Is 107 degrees cool enough? Or should I be looking for something lower?

What number am a shooting for as far as the heat sink temperature.
I wonder what the optimum heat sink temperature is for efficiency of the inverter??

Marshall

That sounds like a good setup and very efficient.

What is the ambient temperature in the garage?

107 sounds real good and should add years to the GT's life.

The lower tempatures will make the FETS in the unit run with lower resistance and hence better efficiency, I can say almost for sure the units increased performance will cover the kW's the fans use over time.