Andy, this is from the rules you sent:
Special Moves(trip, disarm, etc)
Roll an attack at -8 to hit against d20+your opponent’s to-hit bonus. If you roll higher, you succeed. If not, combat continues. If you’re using a weapon designed for the purpose (a sai to disarm, chain to trip, etc.) then roll attack -4 instead.
The way I read it, if he wants to grapple, he rolls at a -8 penalty, and I defend with a 1d20 + my melee. I beleive you wanted me to roll with the penalty. Why? The defender should generally have the advantage because there's no "improved grab" feat, right?