im having to use back heat (its what my rack has) and the thermostat is having to be set at 105 (thermostat probe is taped to the flexwatt) for me to even get 86.5 on the probe outside the bin and 84.6 inside the bin at the back on top of the substrate. Its taken me since yesterday to finally get the temps up closer to what we want... i was just unsure as to where we need to level off at