The smell of burning ear hair made me think someone was talking about me, and sure enough here you are discussing Ilsa'a fuel cooler. Regarding performance, I will say that it has noticeably reduced tank temperature, especially so in hot weather, as witnessed in the motodebauchery of 2016 in the desert southwest in temperatures running as high as 115 in the shade(when shade could be found).
I put it in the return line for a couple of reasons:
First, I wanted to cool the fuel just prior to it going back into the tank because most of the heat is picked up in the rail, fuel pressure regulator, and the return line. I wanted to cool the fuel before it got between my legs, not after it had cooked them.
Second, being down stream of the fuel pressure regulator, the pressure in the return line is only high enough to flow back into the tank. In the supply to the rail the pressure is 35 psi. I go by the philosophy that it's best to minimize the amount of plumbing that is under pressure.
I used an extruded, fairly heavy wall aluminum unit for two reasons:
First, it would be able to handle any high pressure it might be exposed to, and second, since it was hanging out in the air in front of the engine, I wanted it to be stoneproof.
The unit I selected had an internal capacity of about 1 liter which gave the fuel a residence time in the cooler of over 1 minute. I figure that the longer it is being cooled, the cooler it will be when it gets back to the tank. Especially important because the shape was not optimum for air flow over it.
My installation works great on the K75 without belly pan, but may not fit a bike with a belly pan, or a K100 because I have put mine in the space freed up by the loss of one cylinder in the K75.
I like film camera's installation, but being hard against the front of the engine may actually cause the fuel to be heated rather than cooled. It may be desirable to modify the grille work in front of it to allow it to be a little further forward of the engine. Also, it might be good to have a heat shield behind the cooler to shield it from engine heat. A simple sheet of thin aluminum should be adequate. Better yet would be to install the cooler in front of the grille in the open air and let the grille afford some heat shielding.