I think I will "wait and see" if the latest configuration needs any help in the filter department.
That previous service on the PEM and blower did
not succeed without my additional filter material.
So I did it again, with even larger coverage and a finer quality furnace filter material.
A long story made short: This was done late last year while waiting on my Model S, so the Roadster was still driven daily as my only driven car at the time. The hot season was over, and so there was nothing to report as to effectiveness until it was tested again for summer 2013. Though the car has been driven less now that the Model S is here, I do drive the Roadster on any other excuse I can find. Typically at least once per week for work commute, and in afternoon and evenings almost daily.
At this point there are no "too hot" indications from the car. On hot days I observe the "Performance" indicatior turns color (red/orange?) as I use the power, but typically returns to white within 20 seconds or so. This looks fairly good to me, and the car does not feel like it has limited power, as did become
very noticable before the filter. It seems the blower is cooling as well as it can now.
When I did the filter material this last time, I tried to keep it simple, and improvised a bit more. I did little or no trimming of the rectangular furnace filter material, and used plastic wire ties and some strong looking nylon cord to hold it all in place.
So far, the "too hot, PEM dirty" issue seems fixed with the updated single motor blower and my "filter dome of protection".
Here are the pics of what was done last: