bathtub load question
The weight of the tub, itself, plus the water in it (figure 50 gallons, (about 375 pounds) although it's usually closer to 40 when displaced with a human body)... and the weight of the person using the tub (If you're kinky, you'll have to figure for BOTH your weight and hers.) have to be calculated to find your load.
It gets a bit more complicated than that since you have only four directed load points, but the basic calcs should give you something to work with when you look at the charts... or preferably, talk to the engineer.
"True eloquence consists in saying all that is necessary, and only that which is."
François Duc de La Rochefoucauld