I think Ron is running a Mission, not the Mi2. I never had a chance to run that car but as far as I know they didn't have lower towers for that car. That's why he may need the longer ball cups.
As far as limiting the Tamiya shocks, it's not needed if you're running the carpet towers. However if you're running the stock towers with the Tamiya shocks, I think you'll need to use some longer ball cups to make length.