Alpha Layers

I've been trying to make some apron textures that are made up of several layers of polygons overlapping each other and blended with alpha channels. For example, one I have has a base 'noise' texture, a lowres slightly transparent phototexture, a texture for the edges of the blocks that make up the apron surface, a layer for the taxiway lines, and a dirt layer for parts that are used a lot. Each of these (apart from the lines and dirt, which are a different shape) is a separate identical polygon.So far, I've been making these with the FS2002 gamepack and the ADDCAT tweaked asm, and its worked very well.However, where I want to place this is right next to a cliff edge (I'm modelling Madeira so the apron goes right up to the edge) which also has objects below, and these are showing through the 2002 groundpolys.Originally, I was modelling these parts with the FS2004 gamepack and using the zbias_x_ texture prefix to make groundpolys, and this solves the problem of part showing through, but I can't use the alpha layers. If I try to make alpha layers, the alpha not only makes the texture it is attached to transparent, but any textures below them too.Here is the same scene as above, but using FS2004 gamepack groundpolys. You can see that the top layer is not only making itself transparent, but is also affecting the 2 layers beneath it. Each layer has a different zbias number and are in seperate bgls.I need to either:Solve the fact that objects are showing through if I use FS2002 gamepack groundpolysFind a way of solving the alpha problem with FS2004 gamepack groundpolys.Any ideas?