If you don't want to loose ceiling height, you will need to remove the celing covering to gain access to the floor joist cavities.
A product we've had great sucess with is Roxul (http://www.roxul.com ... read more
Depends on the specific type of tub but they can very quickly get over 300lbs.
I have thrown out my back moving them out when they were broken into two pieces so they are not light. Some run as heav ... read more