Hi Steve:
For inspection during FS Development, you may wish to set FSX GUI menu sliders for Terrain mesh at 100% complexity
and the resolution of the terrain mesh file to be used with the custom scenery
ex: 10 Meters between elevation data points on the ground for either of the OrbX payware / freeware packages (or less ...depending on what custom terrain mesh BGL you personally intend to create and supply).
Also, since you are loading the OrbX Yosemite freeware which uses photo-real textures, be sure to
save your inspection flight scenario, and
tick the check-box to make it the "default flight", so that FSX will work with the Windows pre-fetch and caching sub-system ...to expedite faster re-loads of FSX (usually seen by the 2nd or 3rd re-load after activated).
Having a SSD drive helps things load much quicker, too.
But otherwise, one can also speed up this inspection process
without fully exiting FSX by opening the FSX scenery library and simply clicking "OK" to force a re-fresh of a flight scenario; if files are "locked" one can usually instead go to the FSX menu while updating
ex: BGL files, then re-load ones saved flight from there.
In some cases, use of "
Unlocker" can help with replacing persistently locked files without having to fully exit FSX.
http://www.fsdeveloper.com/forum/threads/compiling-without-closing-fs.22667/
GaryGB