Hi,

I had the same struggle with my Vettre scenery http://home.online.no/~roa-kr3/s2.htm.

I do not know about any obj editors, but make sure that your flying line is about in middle of you 6144x2048 frame.
When I edited my base picture ( the 6133x2048 frame) I had to put my 360 panorama picture ( output from the PixMaker program)
into the frame so that there were a gap from the bottom of that picture to the bottom of the frame. See attaced picture, where you can see the line for the extra ground I had to fill in. I used the MSV obj files.

Good luck!