Hi pazuzu
I'm no expert - I'm more of a "work out what you want to see then try to find the commands to do it" sort of guy. My suggestion would be to not even bother with the bomb.
Instead, you could just have the A-10 fly over the target at a suitable height using a simpe waypoint, then have it set off a trigger as it passes a point somewhat short of the wall. This trigger would run a sound ("falling bomb"), then a delay, then you just camcreate the laserguidedbomb right on the wall. Easy as !
This way you get the bomb exactly where you want it, when you want it and you get the approprate sound effect too. I've used this method to simulate an artillery barrage (with the appropriate fire delay, drift and scatter routines included) and it's been pretty good.
Hope this helps.
Roni