@ adriatico, the reflective settings are exactly the same as in the SHIII version, one thing that has been brought to my attention is that SH3 Commander settings may be causing some problems with the SHIV version, if this is so there is nothing I can do about that except to say don't use this feature in SH3 Commander.
For those who wish to play around with the settings you will need minitweaker and this updated scene.dat txt file:
http://www6.rapidupload.com/d.php?file=dl&filepath=37127
The settings to tweak are as follows,
stock shown.
General Environments Data:
ReflBias = (SH3 = 0 SH4 = 1)
ReflDeformation = (SH3 = 0.7 SH4 = 0.35)
Wave State 1:
Amplitude = (SH3 = 0.8 SH4 = 0.035)
FresnelCoef = (SH3 = 5 SH4 = 6)
Wave State 2:
Amplitude = (SH3 = 0.26 SH4 = 0.035)
FresnelCoef = (SH3 = 5 SH4 = 6)
Wave State 3:
Amplitude = (SH3 = 0.22 SH4 = 0.04)
FresnelCoef = (SH3 = 5 SH4 = 4)
Wave State 4:
Amplitude = (SH3 = 0.15 SH4 = 0.09)
FresnelCoef = (SH3 = 6 SH4 = 3)
Horizon:
ZMax = (for 8k = 1000 for 16k = 2000)
The setting that causes a black sky is:
General Environments Data:
LightColor = (any change from this up or down causes the problem)
@ Rik007, try playing around with the
ZMax settings, may also want to change:
General Environments Data:
EarthRadius = 800000
Before modding backup your files & please note that a file "Copy of Scene.dat" will be created in the data folder after modding, this file must be removed or deleted otherwise SHIII will use this over the newly edited file!

Please post your findings for others to compare & share.
Cheers.