How can I correct elevation problems?

I seemed to have read some where, that photoreal sceneries don't work the same in FSX like they used to in FS9. Meaning, that if you had elevation problems, all you had to do in FS9 is make sure your airport sceneries or any other scenery was set at a higher priority level than the photoreal scenery. However, it doesn't work that way all the time in FSX.The problem I'm having is that I have the entire NYC MegaScenery Earth City Pack, along with that I'm using Imagine Simulation LaGuardia Airport, and FSDreamteam JFK airport sceneries. I also have Aerosoft Manhattan X, but I'm not having any problem with this one, since I don't have to worry about landing in Central Park! I do however, have problems at the two major airports. The MegaScenery Earth textures are either bleeding through some of the areas of the airports, while in other areas the aircrafts and other objects seem to be sinking into the ground. I'm assuming this is a mesh problem, but what do I know. If I did, I wouldn't be here asking for help.The unfortunate thing is that MegaScenery doesn't have a support forum like this one here. I've posted a similar question at FSDT forum, but haven't heard a response as of yet to see if anyone there has any ideas, and of course, ImagineSimulation doesn't have a dedicated support forum neither. I hope some of you are able to shed some light on this problem, or if you have used the combination of these sceneries, how have you resolved it.Thank you!