Runways and Taxiways with SU

Hello guys (noobish Q here),

how exactly do you guys export a RWY from SU to be used in the sim?

Explanation: I did a project and designed the entire ground layout with SU. I textured it and exported to MCX then with GP Wizard exported the bgl for the sim. Problem: I see the entire layout nicely but I taxi on dirt. It's like only the textures are placed on the ground but no supporting "tarmac" below.
To fix thix I tried to create the entire layout with ADE without "drawing the surface" that I have an invisible supporting feature below my textures.

Any god hints for me?

BR, Gerald
What you did with ADE is what I do, but I do draw the surface - it is hidden under the ground polygon anyway. Perhaps that will work? Make sure they are all concrete or asphalt.

If you are still getting dirt underneath, remove the GP BGL file and check that your ADE surfaces are actually being drawn.
Thank you. I thought it can be done bether, somehow directly from SU.
If I have drawn ADE surfaces below I had to offset the GP quite a lot to avoid that flicker (textures fighting to show). The wheels of smaller ACFT were half sunk into my GP.
I like ADE alot, but I think i'd rather do it with SU, for the ease of drawing and not having to use a helper to make a curve. just easier and nicer result. also SU ground poly vs. ADE ground poly, it have extra 8-9 fps with SU.
you can actually see how your layers look while you're adding them too.