One thing that helps us in college determine the tackle box parameters is making sure the U/C spots the ball at one of 5 lateral positions. Left hash, left upright, middle, right upright, right hash. So, if the runner is down between the right hash and right upright, put it at one of those two spots and not in the exact spot where he went down.
What helps is that each position gives you a pretty good rough estimate of the lateral confines of the tackle box (or in our case, the FBZ). So if the ball is spotted on the left upright, the left side of the pocket is the left hash, and the right side is the middle of the field. So, if you happen to lose your bearings during the play and you're unsure if where he threw the ball was in or out, you can use those landmarks to assist you. I've verified this on film and it's almost spot on. If the U/C doesn't use those lateral spots for the ball, then you're SOL.
Now, I'd like to see how this lines up with the NFHS fields where the uprights are slightly wider and the hashes are slightly wider. Do we keep 1-5 or do we need 1-7? I'd like to see some film from an EZ angle to determine this.