possibly to late but ive seen someone remove the canvas by pulling the inner ceiling wood off the upper fibreglass bit extreme..
the source was either a well documented restoration with pictures, or a you tube somewhere on internet
the dropped section is the wood that the ceiling wallpaper glues to, my first method of removing canvas having removed all the pesky screws before realised with Agger the canvas slid out that 1st pesky canvas removal method is on the 10 year restoration forum blog written to help others not make same mistakes,
can say the upper metal canvas rail with all screws out did sort of go ontop of the cross brackets that hold roof up
the fix would probably be to remove the canvas by sliding out, remove the pop roof from eriba and lay upside down ceiling upward to reglue and clamp to the fibre glass, jandi may be able to help with a glue.
good luck
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