Okay, here is the final conclusion to this thread. With the help of many good people here and elsewhere I was able to definitely determine that all the problems I was having were due to CPU overheating/throttling and nothing else. It took me a long time to properly understand this because of my own lack of experience in this area.  

The CPU and other chips are covered by a metal plate for heat dispersion. I did not have the confidence to remove this as described elsewhere but the plate got quite hot and that told me that heat conduction to the plate was probably adequate anyway. So I just glued some heat sinks to the plate using thermal adhesive. This reduced the operating temperate but not enough to prevent throttling.  

The other side of the circuit board also got quite hot so I placed a thermal pad on that and covered it with heat sinks as well. This reduced the operating temperature about 10 degrees, bringing it down to the low 70’s. This was right on the edge of what the CPU could handle. I then added a small fan on top of the heat sinks and the temperature plummeted another 20 degrees.

Operating temperatures when fully loaded are now in the low 50’s and there are no more problems. Everything works perfectly when streaming and recording. Of course there are now bits and pieces sticking out the top and there is no way I can get the cover back on but I don’t care. At least it works at last and I have it tucked away where it can’t be seen anyway. The fan is also completely silent.  

On the basis of this experience I cannot recommend the Pipo for anything. The design is terrible for temperature regulation. But if you want to do what I and others have done to improve that, it can at least be made usable.