Mr. Blue and Ms. Red live next doors. Their houses are simple. The walls are one stud wide, the ceiling's one plate thick, some slopes on the roof.
Now they want to move their houses wall to wall. Mr. Blue bores a hole into the wall and happily bolts in a big peg. But Ms. Red thinks that's just a big eyesore!
So they try to hide some clips in the ceiling, but as it turns out...
...they leave a gap one stud wide.
And they don't fit onto a stud. They need at least one more layer of plates in the ceiling.
Okay. That's how I understand the situation. You cannot use Technic bricks (one can see them on the inside), your ceiling's height is just one plate.
So, why not go on top of the ceiling? Up onto the roof, between the slopes and hide some clips or hinges in a chimney or under an antenna?
Just two ideas, the yellow plates represent your ceiling layer.
Fun fact: here the amount of clutch depends on the length of the blue antenna's tip; slide it up to adjust.