I tried thermoforming the top of the skimmer body to provide a transition between the body and the collection cup, but it didn't turn out too well so I won't go through all the steps. Here a few shots that outline the basic process (which still needs some work).
I made a box that would fit over the skimmer to heat the top using a heat gun. The temperature inside gets pretty hot during the initial tests! I believe the range for acrylic is around 300F.
I placed the box over the top of the skimmer and heated for approx 20min at 300F. Here is a pic with the lid off. I used the lid as a damper, leaving a gap, to regulate the temperature inside the box. A baffle was placed inside the box to prevent overheating the acrylic.
There was a mold on the inside of the skimmer which I made from foam to mold the shape. However, the acrylic would just not bend the way I would like it too. Eventually a gap started forming between the top of the chamber and the PVC union.
The top was cut off
and a new one welded back to the skimmer. I will go with a flat top for now.