Jamie,
We don't recommend that you put the probe right on the heat source. Many times it will confuse the thermostats you are using. For example, if you had a stove and the the thermostat probe for the stove was set directly on the heating element your items would never heat because the element heats and cools so quickly it will not warm the oven.
I would recommend starting with an empty rack, place the bedding or newspaper as you would for your animals. Set the probe at least an inch away from the cable set your desired temperatures for the hot spot. Once it reaches the desired temperature, check the hot spot in the tub to see what that temperature is. It should be a little warmer than the temperature you have set on the thermostat. So, now that you know the difference between the actual hot spot and the setting you have, simply adjust your thermostat to accommodate the difference. Check temperatures regularly.
I am sorry you are having trouble, we have worked hard on trying to establish you as a happy customer, and we will continue to do so.
Once again, with rack systems it is common practice to have only a hot spot while the rest of the tubs have a gradient to the front. Heat cable has been used for years in this business; I think it is just an opinion of how much heat some want versus others.
We have also just designed our racks around flex watt, 3 and 4 inch, for some who think it will perform better.
I did research on your profile with us; the only rack I could find with heat was the one I just sent you. Are those other racks you mention with the cable ours?
I agree with Alice also, digital thermostats will vary, be careful.
Thanks,
Mark Mertens