Now I only have one question left regarding this matter.
The dimensions of the texture in the Internal engine ( Attachment), how do I set it in the master_GDL_mymaterials.gdl file?
Extract from master_GDL_mymaterials.gdl:
DIM	tmp_LWA_COGSMASKEDIMAGE_BASECOLOR[3]
        tmp_LWA_COGSMASKEDIMAGE_BASECOLOR[1] =      0
        tmp_LWA_COGSMASKEDIMAGE_BASECOLOR[2] =      0
        tmp_LWA_COGSMASKEDIMAGE_BASECOLOR[3] =      0
DIM	tmp_LWA_RFPLASTIC_SPECULARCOLOR[3]
        tmp_LWA_RFPLASTIC_SPECULARCOLOR[1] = 0.6980392336845
        tmp_LWA_RFPLASTIC_SPECULARCOLOR[2] = 0.6980392336845
        tmp_LWA_RFPLASTIC_SPECULARCOLOR[3] = 0.6980392336845
define texture "Texture142" "Ikarus01",          1,          1,  512,          0
define material	"PKSIkarus01" 20,
	         0,          0,          0,
         0.73,   0.8,  0.06,     0,   0.64,     0,
	  0.921569,   0.827451,   0.972549,
	         0,          0,          0,
	         0, ind(fill, "Background"),    -1,
	ind(texture, "Texture142")		ADDITIONAL_DATA	LWA_COLOR = "LWA_COGSMASKEDIMAGE",
        LWA_COGSMASKEDIMAGE_BASECOLOR = tmp_LWA_COGSMASKEDIMAGE_BASECOLOR,
        LWA_COGSMASKEDIMAGE_FILE = "Ikarus01", LWA_COGSMASKEDIMAGE_SCALE = 0.3000000119209,
        LWA_COGSMASKEDIMAGE_ASPRATIO =            1, LWA_REFLECTANCE = "LWA_RFMATTE",
        LWA_RFMATTE_AMBIENT = 0.7300000190735, LWA_RFMATTE_DIFFUSE = 0.8000000119209,
        LWA_TRANSPARENCY = "LWA_TRNONE", LWA_TEXTURESPACE = "LWA_TSGSREPLICATE",
        LWA_TSGSREPLICATE_SREFLECT =            0, LWA_TSGSREPLICATE_TREFLECT =            0,
        LWA_TSGSREPLICATE_SSIZE = 0.03500000014901, LWA_TSGSREPLICATE_TSIZE = 0.03500000014901,
        LWA_TSGSREPLICATE_ANGLE =            0, LWA_PIPELINE = "LWA_PLNONE",
        LWA_DISPLACEMENT = "LWA_DPWBUMPMAP", LWA_DPWBUMPMAP_FILE = "Ikarus801",
        LWA_DPWBUMPMAP_WIDTH = 0.03500000014901, LWA_DPWBUMPMAP_HEIGHT = 0.03500000014901,
        LWA_DPWBUMPMAP_AMPLITUDE = 0.1000000014901, LWA_DPWBUMPMAP_SOFTNESS =            1,
        LWA_DPWBUMPMAP_SCALE =            1, LWA_DPWBUMPMAP_ASPRATIO =            1