Originally posted by Jesuispeure:
Yeah, that also doesn't work because just holding down the shutter button half way, the lens freaks out trying to refocus itself along the way. So the best solution is to increase my focal plane?
If the camera is refocusing as you move, that would suggest it's in AI servo mode, when you probably want it in one shot mode. I don't have experience with the rebel, so I don't know if that's an intended limitation of the camera or user configurable.
You could probably go nuts doing the math to really figure out how much play you have at various apertures, but the proof is quickly found in the pudding. If what doctornick suggested doesn't work (there are times...), and you get the focus-recompose method working (i.e. getting your camera in one shot af mode) then you can try it out and see what works for you. You might also brave manual focus; you might surprise yourself.