It's A new stunt park built up the sky at 350 ft to enjoy space and comfort, it's above the 2nd city that is the staunton island and a bit on the shoreside vale and it has entries from wichita gardens (3rd city) and Aspatria(stadium coast)(2nd city).
Since there is no gta.dat open it with a text editor and scroll to the end. There should be several lines that end in IPL at the end add this line:
IPL DATAMAPSskystuntpark.IPL
Save the file and it should work