That wont dissipate heat, it will magasinate it.
In between the battery and the SoC, a flat piece of alu does not a whole lot other than direct heat away, and into said alu.
If they wanted to dissipate, they should have carbon-tube film leading to the sides, where the whole side is replaced by a heasink.
Then again, thats where your hands are. There is a tiny bit of space in the front, but its not ideal given the angle you holde the device at. Heat rises back into the case.
Edit: I see the second now, that will work. If they bend the sides of some added material up they can utilize the most valuable space very easily.
A metal battery-cover for the Pyra, with some way of directing heat to it, would be good. Dont know if it interferes with any signaling though. Needs an isolator between it, and the battery. Could groove the underside of it, and even add a few mm of thichness.
The trick is to direct heat through the holes meant for the clips of the battery cover, or similar. If each moduleboard comes with two pieces of carbon tapes attached, you slide those down into the holes as you screw down the mainboard to the case (after clicking in the moduleboard)
If its rigid, but has kinks in the right places, all that remains is a similar process of attaching it to the metal plate.