+40 to your STR check to bullrush someone is still pretty damn good. That's the equivalent of a STR 90 modifier.
You know you've been hanging around CO too long when you see that and think "huh, is that it?"
doesn't matter really, you only need to push them back 5 feet for dungeoncrasher.
you
are above them, right? right?
although long domino bullrushes are fun too, but then a mere +40 mod is sometimes too low for the real fun stuff. hell, even assuming your opponent only gets a 10 on the check, and you get a 70, that's only 5+60/2=35 ft of knockback to work with. a max of 7 dominos.
EDIT: silly me, that's 1+60/5 squares, so 13 dominos max. eh, not too shabby, assuming you beat them by 60. of course, the terrasque would (+31 mod) lose by 39, and get pushed back only 40ft.