Or you can do a recent dodgy I just did last weekend. I cut mine out.
The original window had been simply cut out by the previous owner (edges still sealed onto top) and he'd had a professional re-sew done with a piece of pvc, didn't notice it till I attempted to remove it, which made my job easier with a sharp blade cutting the stitching away.
Had to remove it as it was too far gone that no amount of polish would fix it (tried about a dozen methods scattered across this forum) and it'd become brittle and cracked in the corner....so anyway back on topic.
I then cut up some pvc plastic from a craft store (I.E. spotlight), using the original window I'd just cut out as a template. Then hand sewed in the top & bottom middle to hold it in place then the top & bottom left, right corners. I then proceeded to seal it with clear silicon (note you may want to rough up the edged of the pvc with sandpaper so the silicon attaches strongly).
Then clamped the top half with two pieces of wood and the bottom half I stacked some bricks under it & popped a few on top to add pressure to the base....yes in short I never took the actual back out...though having installed a style bar a few weeks earlier, it's would have been HEAPS easier to do with the bar removed.
I can at a later date then sew more in as I please, but it's holding quite well, and it was just a dodgy so I could see when reversing and until I pull my finger out & by a Robbins with glass backing.
Yes we MX5 nuts are an ingenious bunch.
