I have been experiencing heavy stutters in the sense of high frame variations (within a second) in P3D v4 and v5 in Mallorca, Menorca and Ibiza. They only happen when (any) airplane is flying over the water around the islands (e.g on final LEPA RWY 06). Over land the performance is smooth. The transition is always exactly over the coastline. I could trace the issue down to the three files LEPA_CVX-Terrain.BGL, LEMH_CVX-Terrain.BGL and LEIB_CVX-Terrain.BGL. If you disable them, the stutters are gone.
I then had a look at them with TMFviewer (s. picture). The stutters appear when the aircraft is over the blue area, which defines the water polygons of each island (there are also exclusion areas and airport bounds in the files). The water poly used is of old FS2004 type (LWM) and it seems that P3D is not efficient in rendering these. For FSX/P3D there exists a different type of water poly which does not induce stutters. Sim-wings (and most other developers) have already used this type e.g. in the Gran Canaria Prof and La Palma Prof sceneries.
Is it possible to get an updated version of the three files? I am not sure if they even are required as I have not seen yet a visual problem with water or exclusion. Without the files, there are now waves at the beaches.
The water poly GUID in the three CVX-files refers to the following entry in terrain.cfg (default and ORBX):
In Sim-wings Gran Canaria Prof the file GC_CVX-Terrain.bgl uses the newer FSX/P3D entry:
// Hydro Polygons - Generic Ocean - Perennial