TOPIC: What is the maximum to-hit bonus needed?

Just as a logical question.

If any part of the silhouette without a number is an automatic miss and any part of the silhouette with a "1" is an automatic miss why even have the number "1" appear anywhere on the monster. It seems like it wouldn't appear on the actual monster at all anyway (counter intuitive to "hit" the monster on an auto miss)

IMO is seems much wiser to simply have the non numbered areas of the silhouette counting as the auto miss in this instance. From a player standpoint it's MUCH better that way than potentially "hitting" the monster and being told "Nope, you hit the wrong part of the monster, that's an automatic failure"

I always imagined the zones were simply an abstraction of a d20 roll. d20s have 1s, so the silhouettes do as well. I never thought it was intended to be taken literally.

Also, a slid 1 could be considered a critical miss and bring bad mojo the player's way if the module were so designed. (I had a D&D DM who kept a whole list of unpleasant things that could happen on a critical miss.)
And there are at least two tokens that state what happens if a monster attacks the wearer and rolls a 1. A charmed player attacking the wearer would probably get the same effect for sliding a 1, so a 1 would still be a useful number to have on the board.