Don, there are some issues, at least for me.
I've just created a fake airport with ADE as close to a lake (even closer) than above. It got just an airport flatten poly and a runway. Everything looked okay after compiling.
Now I imported the ADE-created CVX to TS Pro as a new project and wasn't able to save it as such (everything was grayed) until I added a single sculpt node (later I deleted it again).
Next planned step: creating a simple boundary. I selected Start -> Blend Poly List and got the message "A blend poly list exists" and whether I want to delete it.
I confirmed this and got the dialogue box where I was asked for the name (preset "AirportBounds 2" was given) and confirmed.
I added the vertices CCW and had to take care not clicking next to the line connecting the last node with the first one. The result is visible below.
Finally I profiled the blend poly and exported the result to a BGL.
Before enabling the test file:
After enabling the test file:
When disabling the file being compiled (exported) by TS Pro and re-booting FSXA the lake is complete again. I've nowhere used any exclusion, TmfViewer shows just innocent flatten triangles
and TS Pro loads its own file without any problem (surprisingly now the original airport background flatten not divided in triangles).
I added a ZIP for playing. It contains all files in compiled form and the non-profiled TS Pro project file. The scenery is only "enhanced" by old FSG Mesh. It's somewhere in Nowhere, west of UTDL (Tajikistan) at the northeast end of the Kairakum Reservoir. The airport has been placed about 600 m away from the shore.
EDIT: Wrong ZIP file exchanged against the correct one.