I was going to suggest that servo. The futaba 9451 is great , but 9550 is better due to lightweight and compact as well sports very close ratings to 9451. Which makes it better in two ways....one weight and size which makes more compact on the body resulting in less weight transfer in turns...at least when its mounted horizontal on a steering servo in the front.
Maybe small , but everything helps.
You also might laugh but when you dont have hrs system and want to save weight and money the s3003 is actually not that bad. Used it on my r40 , its as fast if not faster than the hitec 625mgs and weighs next to nothing and uses low power.