The pump has arrived! Thank you Preuss Pets for your help in getting the pump for me.
I hooked it up last night and it instantly overflowed my skimmer. The solution was to clamp down the airflow. My understanding is that as the pump settles in the airflow can slowly be increased, which should decrease the amount of bubbles coming out of the outlet pipe of the skimmer.
I also had to make a slight modification to get the pump to fit snugly into the skimmer body... I had to add a small piece of rubber between the hole in the skimmer and the original rubber gasket to act as a shim (sorry no picture). Then I had to put an O-ring to seal the tiny space around the new rubber piece where microbubbles were escaping. Here's the O-ring picture
All in all so far I'm very impressed. The pump is much quieter and produces a lot more fine bubbles than the original Sedra3500 and it uses only 11 watts (compared to 35 with the Sedra).
I'm still playing around with water height and airflow but I can already see how much better this pump is compared to the stock Sedra. For anyone looking to replace a Sedra pump... I highly recommend the Tunze hydrofoamer series.