Relative size mods for Monsters

[Blind Mapmaker]

I've been using tbone's method for years now and it is really much more intuitive. The intention of the GURPS books' authors is of course to use the rules as written. A Hill Giant that rolls against 11 to hit a human is probably more realistic, but it presents a much lesser threat, one that some lucky delvers (and every delver needs Luck) can probably tackle without taking too much punishment.

It all depends how you want to use the monsters, but generally speaking an experienced part against a single, easy-to-hit opponent with no special defences is not that much fun if they also can't hit reliably. On the other hand, if every hit is a possible death check for your novice heroes, it can be quite a tension-filled fight. Your mileage may vary.