chopping a top
years ago we chopped the top off a brand new sport coupe (can't mention the brand). Despite plenty of reinforcements and a lot of $$ spent at a professional vehicle fabriation shop, driving it over bumpy New England roads was always a real disappointment. It handled like mush. But it was good enough for what we were doing, and a cabrio version did make it into production 3 years later with some of the tech we developed on that bastardized car.
It's hard for me to believe any E9, which is torsionally far inferior to any modern coupe, could be opened up without a huge compromise to the driving dynamics. Without the 70's vintage BMW handling all you'd be left with is a proverbial dumb blonde. Apologies to those whom I've just offended.
John