I'm using a 6ft Walco box blade(with scarifiers) on mine without problems !
A 6ft blade will be fine for your tractor ,
How big of rear blade for a CK20S Hydro. THis will be used for moving snow and dirt.
KC
I would check with a dealer and purchase a rear scrape blade, (6' or 7') that I could rotate. A blade that is to long will strike the tires and lift arms preventing you from rotating the blade to push snow and other light materials in reverse with. Also look at the weight of the blade. A light blade will bounce and leave a wash board look.
i'm sure your ck20 would be able to push a 7ft rear blade !
I would REALLY check into that before making that purchase. I mean REALLY check into that. I run a 7ft. blade currently and I wouldn't touch a 7ft. blade with a CK20. To big, to cumbersome, to wide. Can it move it, lift it, etc. Probably, but why use a hacksaw to cut butter . . .