2.4kg/cm means thats how much the servo can lift on a 1cm arm btw. so it would be just 0.24m nm (newtons/metre). servos haven't been trialed enough for bw's to really know what kind of torque is required but in antweights the smallest servo you can really get away with for speed hacked drive is 0.9kg/cm. over 5x the weight of an aw in g/cm.

long story short, better to go overkill with the kg/cm imo. the difference in weight/price really doesn't matter unless you're especially tight on weight.