MidGALandscaper,
I just got my 3520 cab with 300cx and grapple bucket yesterday. The SCV is laid out like yours. The two grapples open and close one at a time for those that want to know. A single joystick control would be nice, but unless you use the bucket all day, day in and day out, you can live with the current controller for occasional use. The grapple bucket has a label on it saying it weighs 590 lbs. I almost tipped over today moving a bucket of mulch. I would feel more comfortable with ballast of some sort on the back. IMHO, its not a bucket you would want to have on when mowing the lawn. Maybe on a 4720 it wouldn't feel so awkward being out there.
I bought the grapple for the specific purpose of picking up large tree branches, and for that task I'm thinking a ballast box would be on order.