This is what I have now: around 3-4mm of space between the tube and the fuse-tailcone mating face.
And a virtually airtight seal at the rear.
My thrust tube came pre assembled, the outer tube has 4mm of overhang over the inner tube at the rear.
Total overhang including tailcone is about 9,5mm.
I was thinking about magnets for gluing the canopy glass...glad to see I'm not the only one lol