I was told by Eco-Tech to ONLY run them in pulse mode to keep the pumps from getting too hot.
My experience has shown in my situation that running on pulse at 100% and a mid-range frequency will create motor surface temps. of between 122F and 129F. There is some variation do to whatever differences exist between the motors themselves, and that's why I give a range.
I also have found that @ approximately 80 - 85% and at a mid-range frequency, they run between 121F and 124.5F as measured tonight on three different pumps with an ambient temp. of 78F.
I also measured my two pumps running @ 100% with dedicated fans, and they were at 102F and 104.5F. These tend to swing between 100F and 109F depending on ambient conditions. And this is why I asked Eco-Tech to attached a cooling fan to the motor.
With a fan mounted as an "upgrade", I don't think any acrylic tank owner would ever have to worry about damage to their tank, provided there was some code to stop the motor should it over-limit. Kind of like a cut-out used on race cars etc. I have no idea what the architecture of the drivers is, so I can't speak to the viability of that idea, but I firmly believe that an attached cooling fan would work VERY well.
Eco-Tech has also stated that the WWD runs the pumps more efficiently and that should translate to cooler temps. but in my situation I haven't had the chance to test that out.