In response to all the concerns about "toxic fumes"
First, let me state that the melting you see on the PC parts may not really be melting. Like I have said many times now, we have not seen it happen on our test units. My personal belief is that it is a stress cracking situation that is exacerbated by higher temperatures. Your missing pieces are probably still there, but fell out of the unit when you removed the PONG and cleaned out the ABV. The reson I say this is that even @ 475F setting, the max temp I have ever been able to measure on the PONG is around 280F. Large temperature gradients between the heater core and the exterior pieces.
I am not looking to get in an argument on that point, we changed the design and material just to make sure we mitigated the risk of damage.
Check the link out on PC's MSDS:
http://web.mit.edu/rocketteam/www/usli/MSDS/Polycarbonate.pdf
Specifically, look at section V health hazards identification. PC is non toxic unless BURNED. that happens at
842F. The PRO can't get that hot (even if the regulation circuit broke, it doesn't have the power to take the material to that temp).