FSXA FIR sectors bisection in FSX Acceleration

In FS9 it was feasible to bisect an FIR sector, meaning that the lower part i.e. up to 11100m and the upper up to 100000m. The lower and upper using different frequencies. It worked fine in FS9. Yet, that doesn't seem to happen in FSX, as, if made so, ATC keeps interchanging those frequencies both for AI and user plane every 10 seconds or so.
Has anybody else noticed it and if there is any workaround to it ? Jim ?

Thanks for your time.
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I am wondering if this "silence" means either that what I was talking about in my previous message actually exists in FSX and there is no solution, or it happens only on my system.
I don't know of anyone else creating ATC sectors?
I am not creating ATC sectors. What I am doing is to change sector frequencies to match the currently used frequencies in the real world and compile with FSX SDK. Then, the ATC uses them in FSX.
There is no better way to describe it.
Thanks Jay.

Problem solved by myself. The entry : minimumAltitudeType="AGL" had to be changed to : minimumAltitudeType="MSL", as, FSX apparently calculates the height from mountains' peaks below, while FS9 apparently does not.