Like me, it probably hadn’t occurred to you that in order for Mercedes to create a roadster version of its popular SLS AMG, it would need to lose the gullwing doors. Okay, it sounds obvious now that I’ve said it, but it still seemed something of a surprise to hear Mercedes announcing as a revelation that the SLS AMG Roadster had proven to be stable even without the gullwings.

The open-top variant is the second car to be developed by AMG on the SLS chassis. The Coupé and Roadster concepts were created in parallel – which brought decisive advantages during the development process, but the AMG engineers have taken 3 years to develop the SLS AMG Roadster, paying particular attention to the aspects of bodyshell rigidity, driving dynamics, the soft top and NVH (Noise Vibration and Harshness).

The roadster deploys the same 563 bhp V8 engine has its fixed roof sibling, and at just 243 kg the bodyshell of the Roadster tips the scales just 2 kg heavier than the Coupé.

Owing to the omission of the coupé roof and gullwing doors, the open-top SLS AMG has a reinforcing cross-member behind the seats which supports the fixed rollover protection system. Further reinforcements are made by a special bulkhead within the aluminium cross-member to provide acoustic insulation for the the 250-watt subwoofer of the Bang&Olufsen BeoSound AMG high-end sound system.

The three-layered fabric soft top of the SLS AMG Roadster, which is deposited behind the seats in a Z-formation to save space, is also an aspect relevant to handling dynamics. It has been designed to handle speeds up to the SLS AMG Roadster’s 198 mph maximum (electronically limited) and can be opened whilst moving at speeds up to 31 mph.

The development team are currently putting the roadster through “accelerated” endurance testing, which sounds as simple as letting a bunch of kids play around in the interior, but actually involves include 10,000 kilometres on the Nürburgring’s North Loop and 10,000 kilometres in city traffic. Where do I sign up?

The AMG engineers refer to these final stages as ‘torture’ testing, which must be reassuring for those customers spending close to £200,000 when the SLS AMG Roadster begins shipping later this year. You can see the results of all this hard work when it premieres at the Frankfurt International Motor Show (IAA) on 13 September 2011.