The age old low to closed cistern (kind of!)

[kevfisher]

So, I’ve changed the downstairs toilet in the old house to a closed coupled toilet. I’ve used a swan neck and it’s about 40mm proud of the wall so going to build it out with some aqua board.
The minor thing is I’m not overalls happy with the fitting from the old ceramic soil to the swan neck. The swan is 90mm without the rubber seal fins and I would say the ceramic is about 95mm I’ve had to cut and fiddle with the rubber fins to get is in but I’m not convinced it’s a great seal.
My question is - is there a reducer or a specific swan neck that I can use? I’ve looked but struggling to find.
Thanks in advance for your help.

 

[Burnerman]

I find that a good spray with silicone lube is enough to get the swan neck labyrinth into the salt glaze without any issues.....I guess the ultimate test is, does it leak when you flush? I’d guess not.
John

 

[Wannabebetter]

Extension A with 2190 bent pan connector? At a guess. A photo of install may help.