It would be better to have a rack that you can strap the kart to.
http://www.harborfreight.com/300-lb-capacity-atv-cargo-carrier-69858.html
I have this. My Invader street kart can strap onto this. I have never used it though, as I could fit the kart into my SUV that I had.
A little bit of modding/ingenuity would make it a perfect carrier.
Uhhhh, he wants a carrier FOR his kart, not to put his kart in one..... The carrier you linked to would make his go kart too unbalanced, as previously stated, and cause the front end to be off the ground the majority of the time....
Op, put a small rack on the front of your kart. Then add a slightly larger one , to the top of the kart. Look at the biggest thing you would ever consider carrying on/with the kart..... That's really where you need to start. What would/will you be carrying?
Camping? Fishing poles, ice chest, tackle box, bait.... ? Tent? Once you figure out the largest, not necessarily heaviest, thing you strap on, you can decide where and how you can/will carry it.... This is one of those times where you really need to plan ahead, so its not too small/big....
Just my 2cents....
EDIT
Just saw your kart..... Forget building a rack to carry stuff. Add the hitch, and build a small trailer to pull behind it. Center the trailers weight, just ahead of the axle. The trailers axle should hold all but 15-20℅ of its load. The rest is tongue weight, keeping the trailer from just flopping off the ball. Your kart has enough oomph to pull a small trailer, and its less wear on the actual kart.
And most likely, and importantly, the safest way to go....
: Remember there is no weight on the front wheels. Good luck whatever you decide.
I agree, but didn't want to be the first negative Nancy. (I think I'm too new to be that guy.) 
and don't mount it behind head rest farther up you go the more leverage you put on it to do a wheelie. if weight is a concern you could always put a caster wheel off the rear of it, as long as you intend to keep the speed down, or make on on front above to foot area but below your eye level, and one on rear. 
when one want work by itself, make two!!!
