We have a Crane San Marcos Armorplus tub, which is Crane's answer to an Americast steel/composite type tub product.
After installation (and they had already started tiling the walls) my husband and I noticed that when you stand in the tub that there is a loud creaking and moaning and noticable flex. Since they hadn't tiled the floor yet we ran a 3 foot metal ruler through the gap under the tub and were able to go all the way to the wall for the full length of the tub--was not set in a mortar bed; tub only supported at ends.
We had a huge argument with contractor who wanted to spray in foam to "fix" the problem. We insisted the tub be pulled out and reinstalled in a mortar bed. He finally agreed.
Now they are pulling out the tub and the tile guy is giving advice to the very young-looking plumbers that they should use "Structalite" instead of a sand mortar (which is what I've read should be used.) Help! What is structalite and is it up to the task of tub setting?? I need an answer fast, if possible, because we are surrounded by fast moving burly contractors now!