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!
I couldn't get a definitive answer on the Structalite question so we insisted on mortar, instead, since I know that is what is normally used. Structalite might work, but I worried about it's lasting properties. It dries hard, but does it crack or crumble after being stood on day in, day out? Also, how does it react to moisture or condensation? These questions being unanswered made me think mortar was a safer bet. Only after it sets will we know if it solved our squeaking tub problem.