Well, I now do the stomp intentionately. It get's in my mind after using, and learning the stomp, also, the triple kill was done in Crash site, when I jumped from the highest building to the spot near the HMG. 2 in Power, 1 cloaked. Also, you don't need really that high things. I manage to do Stomp kills from a glasshouse to the ground. Learning by doing

Also, you have to look for opportunities, like people standing underneath you. Don't shoot, stomp, and before you stomp, activate armor for a better effect. Or you get shot, but you got in cover. Climb over the cover, flank the enemy, and give him a powerfull stomp in his head.
What's your Gamertag? I'd like to show you, when to use, and when not to use... otherwise, it's somehow impossible to do, because you can't always follow me :O Wish I had a capture card but... I'm not a millionaire...