GMax for ground polygons

I was doing some test on using GMax for my groundpolygons, but while doing that I discovered that the frames are lower then when I use the SCASM version I made before.I have the polygons in a DXF file and I imported that into GMax. After exporting it to the ASM files, I edited the source to have the shadows displayed correct.But when I loaded this file in Fs2002 I noticed that I had lost 4 frames (22 to 18) and I hadn't even added all the polygons that were in the SCASM file (the one that gave 22 frames).So, I think that using GMax for the ground polygons of a big airport is not a good choice, as you can get better frames by splitting the polygons in different Area's and thereby controlling the visibility better.Arno