If you put the bypass filter in line with the cooler, you aren't going to get much flow which would negate the usefullness of the cooler. I would suggest paralleling the filter with the oil cooler itself. That way the pressure differential from the input to the output of the oil cooler will force oil slowly through the bypass filter and you will get good cooling and good filteration. This is just one of several ways to do this. If it turned out that there was not enough flow through the bypass filter this way, you could always put a little restriction at the input of the cooler to increase pressure. You will easily be able to tell if it is working right by the temperature of the filter.