reginos:
Do you think that if Porsche allowed the Cayman to race with the RSR engine ( and releasing the corresponding road cars), things would have been different?
A difficult question to answer Reginos. On one hand some of the weaknesses of the 911 platform would be alleviated or eliminated. Excessive tire ware (especially rear tires) seems to be an ongoing issue with the 911 platform. It also seems that when the tires do go, they really fall off a cliff. A quick analysis of the lap times yesterday shows that the 911 is quite inconsistent when compared to the F458 platform. The Ferrari's are able to put in consistently fast laps whilst there is quite a fall of in lap times especially towards the end of the stint, for the 911's. The Cayman platform would no doubt be more balanced and this issue would be reduced or even eliminated.
The second issue is one of engine: Not having DFI is a major handicap (in relation to the 458's) . Shorter stints are a guarantee to having more pit stops , especially in long races like Le Mans. Although the DFI advantage has been reduced by the ACO giving smaller fuel tanks to Ferrari, there is always some advantage gained from lower consumption. (shorter fuel stops).
Another engine related issue is that of torque: Although Porsche insists that the old Mezger is still capable of taking on the opposition, the truth of the matter is that the Porsche's are no longer the cars with the highest top speeds.(3.2 Km/h slower than the fastest Ferrari). This will be a killer at Le Mans. I have no analysis of the acceleration figures, but it would not surprise me if there was a deficit in those figure as well.
The final issue (in this post) is that the increased wheelbase of the 991 seems to have improved the stability of the 911 in the fast corners. A Cayman platform would be a regression in this area.
All in all, Porsche know the strengths of the opposition. They also know that today's GTE cars are almost real racing cars. They have painted themselves into a corner by insisting that the 911 platform be the only GT platform that they will consider. It is indeed remarkable that Porsche engineering has been able, throughout the last 50 years or so, to overcome the shortfalls of the 911 platform, but times have changed . The opposition has changed. They have come on strong and they are not chained to using one particular platform. If for example, Ferrari found that the 458 was noncompetitive they could (if they wished) come out with a completely different car that would counteract the short falls of the 458 platform (if they existed). Porsche seems to deny itself this freedom. These days the company seems more interested in selling than in winning. I hope that someone remembers that without winning; you do not sell. Not in the long term anyhow.
Finally; I really hope that Porsche has not underestimated the competition with their LMP1 project. Another failure in that program could place the remainder of their racing credibility at stake.