My girl was previously in the T8, and I had the shelf as well. In MY CASE she wasn't using the shelf. So after a year's time, I removed it. I think if yours is climbing and uses it, I see no reason not to use it. Keep it in there. However, there's always stuff you can add in the center to climb. Either way, if you decide to leave it, you need to find the hottest zone, and then keep playing with the thermostat so that the hottest area is not too hot.
When I was testing mine, I was using a Herpstat 4, which has 4 probes. The heater was connected with one of the probes, and other 3 were just in there to easily measures temps all around the enclosure. If you have additional thermometers, you can spread them around the enclosure and do the same. Will take some time, but you are doing it right, testing now before you actually put it to use.