Having problems with heating my t8's.

So, I'm trying to achieve a hot spot of 88 degrees in one of my new t8's using heat tape. I have my thermostat set to 90 but the hotspot won't go over 79 and often during the night it drops to 76 or 77 which is the ambient room temp. I have measured it with a digital thermometer and a temp gun. I don't have this problem with the cage directly below it and the settings are the same. If I take the gun and measure the temp through the ceiling of the bottom cage it reads as 87-88 which is what i want. This might be a stupid question but is it possible to install the heat tape upside down?

I don't have heat tape on my T8s but I'm surprised you get your target temp with 90F on the lower cage. I've heard most people say they have to set their thermostat to 100F to get their target temp inside. Do you have an issue with raising the tape temp?


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I think I found the problem. The bottom cages thermometer was super wonky. I replaced it and now both of the cages are reading at the same temp. I raised the thermostat to 98 degrees so hopefully that helps. Thanks!