a) Bubblehead's way is the better one, so use his. Or mine. Whatever you prefer.
b) FS9 mesh is fully compatible to FSX.
c) If you downloaded the world mesh for FS9, you wasted your time. In most regions of the world, FSX features a default mesh of 76m (even better in some places), so a 76m add-on mesh wouldn't make much sense.
But it's up to you.
