RB also fillet the junction of the diffuser strakes and the upper inside surface of the diffuser. As I mentioned in a previous thread, those fillets look like a very thorough attention to aerodynamic principles in even very small details. The junction of two perpendicular surfaces will create what is called 'interference drag,' which can be non-trivial. To overcome this, the junction is filleted, as shown in these photos of the great and beautiful Spitfire. (These metal surfaces, and those in the elliptical wing, however were difficult to fabricate.)shelly wrote:...
-the big fillets at the junction between floor and strakes (other teams do not have them)
...
and 
I suspect the exhaust strake filleting also delays the dissipation of the vortices shed by the leading edges.
