I started a project where I used fighter spawns to set all of the fighters in the game, and some bombers, on the edge of slopes surrounding a small airfield so I could use 6 of 8 spawns. Ended up with three small islands and three airfields with 18 spawns to cover 95% of all the rides. Turns out it is a large scale bite in the whatsis to adjust the terrain to have a fighter spawn on it and not break its back while resting with the center line level. So surrounding these feilds are pits that run off into the ocean.
The rational for this is the center of the .Target is aligned with the center line Hitech assigned to each aircraft regardless of pitch. So I end up pulling the target all the way in to let prop HUBS or obvious center lines show me how much I have to raise or lower the pitch of the ground under the spawn.
Once this is accomplished, I spawn out the plane, pull up the target at say 400 and look at the relationship of the center line\target center to the center of the gunsight and the impact point on the target. I'm a few planes short of being finished and I'm fully involved with my new Melee arena terrain I've been documenting in the Terrain Editor forum. Besides, setting a plane on a static stand to bore sight like this does not show where the IP point will be relative to the gunsight influenced by your speed, turn rate and nose pitch during combat. Only combat experience does. A better thing to see can be done by sitting on the runway and pulling up the target while adding positive pitch to put the target up into your gunsight. Then at 200-600 look at what your impact spread will be. Also, this setup will not show you how much gunsight elevation you have to use flying a level 6 chase to land rounds in your con .25sec after you pull the trigger at 400yds. Only in game experience teaches that.
Here is a P51D on a static stand. All this verifies is the bullets are impacting relative to the center of my gunsight at 400yds, the rest is eyecandy. And way more work than it's worth, or Hitech would have coded a hard stand into the convergence app to let us test exactly this. And I don't like using the thing now that I created it because it shows you can tilt the motor mounted cannons in fighters up through the engine which is impossible outside of this game. In real life they were bolted in place to the engine firing straight out of the HUB.
You can also pull up terrains offline and look for slope drop offs at the ends of runways, then inch your ride just over the slope. You use the target in F3 mode to inch the center line into position. That's what I did for a number of years with the TA terrain offline.