After having the dual solar panel running for two weeks then sending it back to acurite to have it back for the Past week I installed my single panel back onto my 5-1. Lot of people think it is a slower fan causing the heat issues AcuRite says they are both the same. I'm thinking it is the Solar panels that actually might be making the extra heat, they are bigger panels and made differently then the single panel unit.
It's not quite the same. The motor and fan might be the same parts, but the solar panels and the way they are wired to the motor are obviously different. It's quite possible the new configuration isn't running the motor at the proper speed. I've heard several reports of people having better results going back to the single panel, so there's likely something awry with the new panels or the way they are wired.
As for the panels generating extra heat that is somehow making its way to the sensor, that's very unlikely. The panels are well above and to the side of the temp/humidity sensor, which is pretty well isolated in the wind-tunnel. Warm air rises and would not naturally flow down the wind-tunnel to the sensor.
Much of the wind tunnel above the sensor is black to help induce an upward air flow through the tunnel via a chimney effect. If anything, extra heat from panels should enhance that effect.
Mounting your unit higher can cause a significant difference depending on your situation.... there's less possibility for influence from ground/roofing surfaces and catching an extra breeze can certainly help if your fan is having problems.