Hi Malte:
In response for you 2 questions:
a) How could I have the portlet closed when calling the page?
Currently you can't, because it is a beta version there are some things that still need to be implemented .
b) To speed up the loading, have you thought about doing it asynchronously for the closed portlets?
That's a good idea!!, I haven't thought about that, but it can be implemented without so many changes.
Greetings