All apologies if my questions have been addressed previously; searching several pages of the forums revealed many threads about the feat, but nothing that I found helpful.
First, the feat itself:
http://www.d20pfsrd.com/feats/metamagic-feats/toppling-spell-metamagic
First point of confusion:
Looking at the Trip maneuver, I notice it states that you cannot trip something more than one size category larger than yourself. RAW would imply that this limitation applies to Toppling Spell (with, say, Magic Missile), but should it?
I've seen several spells that allow you to make combat maneuvers against enemies, but size modifiers aren't always taken into account, leading me to assume that most spell effects are considered to be "medium-sized" unless otherwise stated. Is that a prudent point of view to assume, or should a Halfling Wizard be incapable of using Toppling Spell to affect an ogre?
Alternately, could a Human Wizard who casts Enlarge Person on himself be able to trip Huge enemies with Toppling Spell?
Second point of confusion:
Toppling Spell states that "If the check fails, the target cannot attempt to trip you or the force effect in response."
Again referring to the rules for Trip, it states "If your attack fails by 10 or more, you are knocked prone instead."
http://www.d20pfsrd.com/gamemastering/combat#TOC-Trip
Trip according to the SRD makes no reference to the idea that an opponent can counter-trip you in the first place (perhaps an oversight from 3.x?). I'm assuming that the point of the text in Toppling Spell is that failing by 10 or more to trip an enemy won't result in a prone spellcaster, but that's not actually what RAW states (and I want to nip any such rules debates in the bud well in advance).
Any help on this topic is appreciated.