New problem
I solved the export to SCASM folder quandary, It seems that there is some sort of security lock on that folder which prevents exporting to it (my UAC is off). Instead I copied the SCASM.exe to another folder and exported to there with no problems. I made the necessary changes to the .sca file according to MR's instructions and created a new bgl.
With the new .bgl in place I started up free flight and sat on the runway. The runway, taxiways and fuel point were all there, in place, but the texture was above the ground, in the air about a thousand feet! My scenery elevation is set at 870ft, so I went back to FSSC and, on a hunch, changed the altitude of the polygon (where the texture is imbedded) to zero rather than 870. I ran tit through SCASM again to get a new .bgland noticed the same "floating" texture phenomenon. This close to success I won't give up...