5.5 acres is a lot of ground to cover for a light craftsman aerator.
My Northerntool core aerator looks identical to the craftsman. Those core aerators do a really great job but are a bit flimsy, consider beefing it up if you can? For an extra $100 and a bit of DIY, you could make that aerator a strong unit from the get go. Mark is right, there is no middle of the road aerator which is a pity.
Before you buy, make sure you have a good look underneath. I have 1 acre and my northerntool unit started to crack and wear after about the 3rd year of moderate use. 2 runs a year, 1 acre, multiple passes (lets say with each run I did about 4 passes in various directions, total area covered about 4 acres if that makes sense...). There are no proper bearings fitted to mine so the shaft ran inside a short piece of heavy gauge tube welded to the side plates. Even though I greased it regularly, it wore into the shaft pretty quick. I fitted pillow block bearings at each end of the shaft on the side plates to up grade it a bit. Also, have a look in the middle underneath where the shaft is supported in the middle. If theres only a piece of light folded sheet metal between the bottom of the shelf and the shaft, then that is most likely going to wear, buckle and crack like mine did. I had to beef up that support with a home made 1/4 plate bracket and I fitted a pillow block bearing there too.
Come to think of it, I adapted mine to fit on my 3pt hitch as I found it a bit of a drag to raise and lower the wheels every time I wanted to maneuver my unit around the place. Theres a lever and pin set up to raise the aerator up and onto the wheels, this is dangerous when the aerator is loaded, if you dont get the lever fully engaged into the slot pefore you fit the safety pin, the lever can pop out and the aerator will drop violently with the lever whizzing passed the operator

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It is a good idea to be able to lift the aerator completely off the ground when you come to the end of a pass. I would recommend you look at an aerator that is 3pt or 3pt adaptable with an aftermarket upgrade.
EDIT: Here is a pic of a pillow block bearing similar to the ones i used. Complete with grease zerk.
hth,
blag