Little Giant Heater Question

Thinking about adding a little giant to my current rig just to heat the water a bit extra on those crusty nasty places. I had a machine that had one inline with the pump and kept eating up the seals in the pump. So I was thinking about installing it so it would be a last step heating. I was wondering if anyone has ever set one up post pump on a machine, and if that would reduce water flow? Do little giants need constant water flow to work properly? Also if I was preheating the water with the exchangers would the little giant run more efficient or just overheat? I know I may have to get in touch with little giant to get some more detailed info, but I thought y'all might have some insights.