Det finns faktiskt en Paragon-sökväg som kan hjälpa till med detta. Specifikt är dess nyttjandekraft "Ride the Giant Down":
Ride the Giant Down
Daily ✦ Martial
Move Action Melee 1
Target: One Large or larger creature
Effect: You move into the target’s space, provoking opportunity attacks as normal. Until you leave the target’s space, the target grants combat advantage to you and your allies and takes a –2 penalty to attack rolls, and you grant combat advantage to other enemies. Any attack that damages you also deals half the attack’s damage to the target. When the target moves, you move with it, staying in the same portion of the target’s space.
If the target hits you with a melee attack, it can slide you 1 square to a square adjacent to its space unless you succeed on a saving throw.
Special: if you are trained in Athletics, you don't grant combat advantage to other enemies because of being in the targets space, and you can make a saving throw to negate any pull, push, or slide that would move you out of the targets space.
Detta är nivån 12 nyttaffekt från Giantslayer Paragon-sökvägen.
Det här kanske inte är rätten du letar efter, men jag trodde att jag skulle nämna det.