Sky’s the limit; as not much else will hold you back.

WHAT IS IT? The convertible-roof variant of the Mercedes-AMG C63 S Coupe, so in terms of price, the new flagship of the C-Class range.

WHY WERE TESTING IT Any opportunity to get behind any variant of Mercedes-AMG’s brilliant 4.0-litre twin-turbo V8 is to be jumped at. But we really wanted to see how much the extra weight and slight loss of rigidity affects the performance of this model compared to the sensational C63 S Coupe.

Mercedes -AMG-C63-Cabriolet -front -side

THE WHEELS VERDICT No question this is a superb 2+2 performance car, however, there is a slight paradox in taking the most focused, hardcore variant in a model range and saddling it with more weight and less rigidity. For buyers happy to take this trade-off in return for fresh air, sunshine, and even better connection with the mighty 4.0-litre twin-turbo V8, we won’t argue. If you’re less concerned with chasing the last gasp of ballistic performance, you may find a better fit with the C43 Cabrio, and pocketing the $60K difference.

PLUS: Roof quality and insulation; ease of roof operation and airflow management; still bloody quick MINUS: Weight gain over coupe; occasional (slight) body tremors; tight boot space with roof down

Mercedes -AMG-C63-Cabriolet -rear -side

These days, the water surrounding ‘flagships’ is a little murkier. Are we talking about the fastest? Or the most expensive? If it’s the latter, then you’re looking at the current pinnacle of the Mercedes-AMG C-Class range: the C63 S Cabriolet. For the buyer who asks to be pointed to the ‘best’ C-Class in the showroom, then $179,900 says this is it. It’s nearly 18K more expensive than the Coupe, and its roof retracts in 20 seconds at up to 50km/h.

Mercedes -AMG-C63-Cabriolet -driving -side

But back to the original quandary: the C63 Cabrio is not the performance flagship of the C-Class range. That title still very much belongs to the Coupe, which retains a noticeable stiffness advantage and, significantly, appreciably more handling precision, thanks to a 125kg weight advantage. Those extra kegs knock the Cabrio’s 0-100km/h sprint back by 0.2sec; Mercedes claiming 4.1sec against the Coupe’s 3.9sec.

Mercedes-AMG C63 Cabriolet interior

But it’s really the perennial cabrio-roof engineering hurdles that the C 63 S attempts to leap that hold it back from greatness. This AMG model gets only the stiffening and bracing measures applied to the other three models in the cabrio line-up, and Aussie roads are still capable of delivering a shake-up that can ruffle it just a little.

Mercedes -AMG-C63-Cabriolet -engine

But the ‘alternative’ facts are these: this is still a relentlessly rapid performance car with a twin-turbo streetfighter’s heart. Knock yourself out.