How to use a remorhaz as a mount

One of the PCs in my party is a half giant beast rider, and wants to have a mount that ties in with his heritage. We all thought he was going for a roc, but once they went to a frost giant village looking for help, and saw their domesticated remorhazes that I was going to use for a later quest, he fell in love with the idea of riding one into battle.

The game we are playing is very RP heavy, and for the most part, everyone loves using the cavalier as their designated thing-hitter, so him being stronger that the party in combat is less of a problem (but I still want it to stay reasonable).

What templates should I use to scale it down to a reasonable strength appropriate for a slightly stronger that average mount?