Unfortunately, I’ve never heard of a good situation where a freestanding heavy bag can be helped to solve every problem it encounters. They have brackets that attach the bag to metal tubes, which won’t really shake unless you dig hard into the bag and throw it away. I have one and never had a problem. You don’t know where your punching bag is, but you can’t seem to find a middle ground right now.
These fund grants aren’t worth much, in my opinion. Those hanging from the ceiling are your best bet. They are popular for a reason. Stand-alone bags are very painful. I say it’s mostly for kids. After all, once you actually start hitting a bag, all the stuffing accumulates at the bottom of it. Thus, hanging it becomes a great help to strengthen your punches, in addition to preserving your bag for longer use.
I wish I had better information for you, sorry.