No, I have to totally agree H.T it did not seam that secure so I tucked the rear in. The sides have magnets built in but they are the most week magnets that I have ever come across.
I would not like to use this, if as you say it rains hence why its never come out of the bag.
I've never seen this type of cover on any other Z3 though.
This type of tonneau needs to be right fitting, strongly secured (eg press studs/pin studs all round) and very importantly must be self draining from the middle to the outside. Otherwise, water will puddle in the middle, swap brought he zip and soak the interior and even unpop the press studs (hence why there are pin studs along the front of the dash under the windscreen. I used a price of wood as a 'tent pole' to ensure the middle of the tonneau was higher than the edges so the rain water would quickly drain away (on my old Triumph Spitfire, but the principle is the same. I totally loved my weather proof tonneau and often drive in English drizzle with just the driver hatch zipped out which also protected the rest of the interior from spray. In my opinion, an essential roadster assessory in England