Baader still has TEC Flatteners for the 140. They advertise them for the 140FL. However, I am readily using it with my 140ED and see excellent tight stars - no blue bloating or something like that. Example: 
For adaption I ordered a custom made adapter from the 6x7 flanch to M42. On the TEC side it is set in place by the locking nut. On the camera side a M42 male thread. I am honest and say, that I don't like the adaption with the locking nut. On the camera side in tends to be too tight and removing the camera requires me to unthread the whole flattener, then removing the flattener and then a pincer for unscrewing the adapter from the camera. But that is my custome made unit. Maybe the one sold by Baader or alike is better.
I think Peter Nagy came up with a better solution, which I am looking to adapt sometime maybe: https://peternagy.sm...g-Train-Setups/
Another option would be to use the thread from the back side of the flattener to your camera thread.
distance from the flattener starts at the notch on the flattener which is covered by the locking nut.
Michael, that's a beautiful picture. Pin point stars all the way to the edge. And way too many galaxy's in your picture to count, nice!
I think those TEC Flatteners for 140 on the Baader site, are the ones that were made for TEC140ED. I'm not aware that TEC made new flattener for TEC140FL. The 0.9x reducer is new which can be also used with the TEC-140ED from what I have seen/read.
Sorry to hear about your custom unit. The custom unit (used for FSQ and ATIK383) that I have (2mm thick) gave me also headache, it was very stiff as well.
From your link and the link that Dwight posted, It looks like that the Baader 6x7 to M68mm adapter is the same as the AP A1260.
To me these two adapters look the same:
Baader 6x7 to M68mm adapter:
https://www.baader-p...c.html?___SID=U
Astro-Physics A1260 adapter:
https://www.astro-physics.com/a1260
With the attached imaging train, If I'm correct, I would need a custom adapter of 18.3mm, though I need to account the thickness of the locking nut.