Thanks for the link to that article. That's too bad they can't co-exist. Sadly, with Orbx Meigs loaded, most of the downtown buildings lose about 50% or more of their actual RW architecture and other critical buildings are simply missing/excluded. And the DD Chicago Landmarks is sooooo good for heli flying (or just plain manual moving around town, visiting favorite spots), just no way to run both UNLESS a person actually wants to only fly fixed wing out of Meigs and quickly leave the area (which I have done several times in the past).
I did find that putting DD Chicago Landmarks just below Global Airports in scenery.ini, I am getting runways/taxiways for Meigs overlaying the newer park area from the Landmarks scenery, so can still use it for a takeoff, etc. Just no airport buildings, etc. For heli pilots, the DD Chicago Landmarks does offer a nearby heliport by Navy Pier, so can easily spawn at Downtown Heliport (CH1) for great waterfront and downtown tours.
SUGGESTION: Since Orbx is now selling this package, I think it would be advisable to clearly mark on both of the scenery pack pages that they are not compatible with each other. Both are great packs, but they apparently can't be made to work together without problems. That at least gives the buyer awareness that the two (sadly) don't compliment each other and cause serious issues. And perhaps someone will come up with a recipe for a cure!
As usual, thanks for the assistance!