Why pay extra? and if the carbon gear was made to be light weight, it may not hold up very well to the harrier landings.
I just added a spreader wire accross the stock gear about 1" up from the axles. I used a 4-40 rod that was threaded on both ends that I had laying around. Working pretty good so far. On really hard landings, it bends the gear below the spreader rod but not enought to touch my 16x4W prop. I just bend it back and fly somemore!
I had a carbon gear on another plane that cracked at the radius after a semi-hard landing. I'll prefer alum gear for harrier landings. Gives me a good buffer.