Uneasy peace among the engine manufacturers?

As the Formula One fraternity gathers itself before the long haul flight to Melbourne, some within the paddock believe not all is as it should be with regards to engines.
Heading in to pre-season testing it was believedMercedes had produced the strongest power unit, as engines are now known, with Ferrari the weakest. It was a conclusion drawn from early meetings of the Technical Working Group whereMercedes lobbied for more aggressive technical controls as the new engine formula was being ironed out, while Ferrari suggested more leeway might not be a bad thing. Sat quietly, and therefore somewhere in the middle, was Renault.
Following a difficult time during the three pre-season tests in Spain and Bahrain it seems it is the French power unit which faces the most questions heading in to the season, but there are others being asked quietly of Ferrari.
There are many who feel Ferrari has not met the design brief which it agreed to as the final engine regulations were penned, specifically Article 5.18.5 of the Technical Regulations which states that "Measures must be taken to ensure that in the event of failure of the turbine wheel any resulting significant debris is contained within the car."
Both Mercedes and Renault built containment shields in to their power units as a result, something it's understood all manufacturers had initially agreed to do, though Ferrari elected not to and has argued it doesn't need such a system because it has designed its turbo not to fail.
The exact weight of the containment shield has been estimated by some at 3 kilograms, though this is open to speculation and interpretation as weight is not specified as part of the regulations. However what we can read into the situation is that Mercedes and Renault are almost certainly a little more bloated than they need be. Unfortunately for them though it's not simply a case of removing the shield and playing Ferrari at its own game as there are safety concerns over its presence - it was the reason it was put there in the first place - and tight homologation deadlines effectively forbade it.
The whole situation is an emotive topic within the paddock and first raised its head in late January. While there was some suggestion Ferrari may beef up its engine in anticipation of an unlikely protest in Melbourne there has been no official word from the Italian team saying as such.
It all means that as teams pack up for the journey south there remains a sour taste in the mouths of those who believe the playing field is perhaps not as level as it should be on the engine front.