Yeah, I know I didn't do well on that post. Here is what I am messing with.
1. Stick down a line of tape on the bed in the exact line you need to be centered.
2. Tape a string with a foam plumb bob ( with a small weight in the center so it will hang plumb) to the center of your cab over.
3. Do the same thing toward the back of the cab over.
4. Now, back under while keeping the bobs centered on your tape and you should be going straight in.
5. Keep going while keeping the back bob over the tape and finish backing in.
6. Remove your bobs and lower the camper and you should be on the money. Just make sure your marks are where they need to be and it should go right on. I just tape the bobs to the cabover so they remove quick.
7. All in all this works well but the job goes well without all this if you just spend the time to run through the basic loading procedure, you will get it down pat soon.
Hope this helps, practice, practice.