There are still issues with controlling the filter wheel from TheSkyX. So, I decided to use the Hyperstar lens for now (if I have to exchange filters between exposures anyway).
I removed the camera, filter wheel and OAG from the scope and moved the lodestar back to the guidescope. Then I removed the secondary mirror. But I unscrewed the wrong ring, and the ring that's inside the corrector plate fell in!!! Yikes! Took me almost an hour to figure out how to fix that again. Once that was done, I attached the hyperstar lens and the camera.
Of course, focus was completely out. It took me a while to figure out the new focus range. After that was done, I could do the 2-star alignment, calibration and polar alignment. Unfortunately, it's not as exact in this setup because of the wider FOV. I didn't bother for now to figure out the right parameters for @Focus2, but focused manually with the Bahtinov mask (furthermore, there is a loose connection somewhere in the Robofocus cables and I had to do the fine focusing manually :-(
Once all that was setup, I started to image M42. I could take Ha and Red images, then clouds rolled in :-( According to the weather forecast, I will have to wait several days until I can finish this.
... weather didn't get much better. So, here is at least a 60sec Ha image (stacked from 21 images, no darks/flats/bias, no post processing):