Maybe you should go read the thread about all the problems with the Tak FSQ106. Some 85’s were mentioned as well. With all your concern about collimation in quads and over, I’m surprised you haven’t chimed in.
Collimation issues and especially problems that seem almost impossible to fix seem to be a recurring theme with Petzval-type scopes. I don't know whether the design is unusually sensitive to misalignment or if it's simply a product of having more lens elements but I've seen that many threads complaining about persistent issues with these type of scopes that I'd be very hesitant to invest in one.
Since I'm only beginning in astrophotography and don't plan on going very far down that rabbit hole, I think I'll stick to doublets for now as a safer bet but still good enough for my needs.
