I did have to reduce the elevator cylinder, but having done repeated test fittings, not by much, just enough to leave top and bottom gaps between cylinder/floor and cylinder/roof the same.
The window frames are delicate, which is fine, but on my kit the fit is not consistent due to tiny variations in the window apertures on the main body.
I built the body before the interior kit was available, so the precise size, uniformity and squareness of the window openings was not something I addressed.
The geometry of a sloping window in a tapering opening was never going to be straightforward !!!
At present my window frames are unused ; I cut acetate for each opening and applied a frame to each using 0.5mm drafting tape. (Cheating !)